Esther Milich Kozminski, 61, formerly of Lodz, Poland, and now from Beverly Hills, Calif., said she lay in bed awake for several nights trying to think of something she could do to carry out her mission.

In Jerusalem yesterday, walking around a bare concrete hall half the size of a football field, she was wearing her inspiration and hoping it would end her search of 41 years.

"I last saw my sister in 1940," Kozminski said. "She was a little blue-eyed girl of 14. I'm positive in 1946 she was alive. Won't somebody please help me? Her name was Hanna. All I want to know is -- is she alive or dead?"

Esther Milich Kozminski, nee Edzia Frymet Milich, was wearing a white polo shirt with her maiden name, home town of 42 years ago and former address emblazoned on the front in bright red letters. She was hoping to catch the eye of someone who had known her in that life so long ago, before fire and madness destroyed her family. In another setting, her appearance might have seemed cute or bizarre. Here yesterday, Esther Kozminski's inspiration seemed grimly appropriate and totally understandable.

Kozminski has come to Jerusalem along with 4,000 other men, women and their grown children for the first -- and probably the last -- gathering of Jewish survivors of Nazi death camps. Old friends and relatives who had lost contact 40 years ago or more wept openly yesterday as they were reunited.

The memory of the Holocaust as the survivors gathered still plays a significant part of the politics of Israel. In answering worldwide criticism of last week of Israel's bombing of a nuclear power plan in Iraq, Prime Minister Menachem Begin vowed: "There won't be another Holocaust in history. Never again, never again."

Although the "official" opening of the World Gathering of Jewish Holocaust Survivors is today, as many as 1,000 of the expected 5,000 survivors (1,000 are already living in Israel) and their children from 23 countries congregated in the Jerusalem convention hall where the gathering is being held to seek out friends and relatives from a world that was utterly destroyed between 1939 and 1945.

The week-long gathering, described by survivors who planned and coordinated it as a "celebration of life and a celebration of our survival," is an event designed to bring together the remnants of the camps where more than 6 million Jews were exterminated by the Nazis.

Ernest W. Michel of New York, a survivor of Auschwitz and chairman of the gathering, explained its purpose at a morning press briefing. "We want to tell the world as a group once more, 'This is what happened to us. We survived it and we pray that it will never happen again -- to Jews or non-Jews. One Holocaust is enough,'" Michel said. "We want to tell the world, 'Don't let it happen again.'"

Michel was at pains to make clear that the gathering has no political platform and no intention of becoming a permanent organization. The gathering, he said, is a "one-time happening that has never taken place before and will never take place again."

A variety of speakers, including Israeli Prime Minister Menachem Begin and President Yitzhak Navon, will address the gathering. Meetings and seminars on several topics of common interest have been arranged. A day has been set aside for the "second generation," children of Holocaust survivors, to discuss mutual problems and concerns. Visits to Kibbutzim -- Israeli communal farms -- founded by Holocaust survivors have also been arranged.

But the heart of the gathering is the opportunity it will give those participating to seek out old friends and relatives from the hundreds of cities, towns and villages where Jews lived in Europe prior to the outbreak of World Was II.

Yesterday hundreds of participants, many still carrying the numbers the Nazis tattooed on their left arm when they entered concentration camps, appeared at the "survivors village" set up here as an assemble point for the event. Desks have been set up for 22 European countries and North Africa so that survivors from those countries can write down their names, town of origin and present addresses on the off chance that someone they know from the distant past may find them. The names of all participants have been placed in a computer so other participants may contact them. In addition, the entire 3.2-million population of the state of Israel is computerized and available for the participants.

In a different sort of life, they might have been coming together for their 40th high school reunion, appraising each other's middle-age spreads, eyeing receding hairlines and chortling over gray hair. Certainly from their appearance, they looked like ordinary tourists who come here every summer from all over the world in leisure suits, double-knits and white shoes. Instead of talking about study hall pranks or teen-age crushes, they talk about the life they had led in their teens -- about forced marches, obliterated families and the day the allies came to liberate their camps. "Oh," said one woman, with a bitter smile, "I was in the good ones. Treblinka, then Buchenwald, and finally Bergen-Belsen." Bergen-Belsen was the "model camp" where the Nazis simply stopped feeding the prisoners the last six weeks of the war, leaving thousands to die slow deaths from starvation. After the war, British soldiers found several tons of unused flour and enormous bread ovens nearby. The bodies of the dead were buried in open trenches, pushed in by bulldozers after the British liberated Bergen-Belsen. The Germans had also given up burying the dead.

Repeatedly throughout the morning, middle-aged and elderly participants squinted at the name tags of other participants, asked a question or two and then screamed with sudden recognition and emotion.

Bella Katz, 57, and Leah Pilecki, 58, both formerly of Vilna, Poland, last saw each other in 1943 when the Jewish population of their town was sent off to concentration camps.

They met again today. "She didn't recognize me," Pilecki said, hugging her girlhood friend while both wept unself-consciously. "I had beautiful blond hair the last time she saw me." Today Katz lives in West Berlin and Pilecki in Little Neck, N.Y.

Abram Stone, now of Los Angeles, and Victor Blumenstyk, of Fairlawn, N.J., liberated together on April 18, 1945, from Langerstein, met yesterday for the first time after having lost contact for more than 30 years. Stone stood in a corner weeping until he regained his composure and was able to talk with Blumenstyk and other former camp mates.

Others, however, were not so fortunate. Jacob Borutzky, 70, formerly of Warsaw and now a resident of a Tel Aviv suburb, wandered forlonly around the hall holding a sign with the name of his sister, Faiga, who would be 80 if she is still alive today. Borutzky said he has not seen her since 1939 but he was told in 1946 that she had positively been seen in Warsaw that same year.

No one who has not had the experience of returning home from a long absence to find family, home and community entirely gone, as though they had never existed, can understand. "I heard my family was deported," Ester Milich Kozminski said in an almost offhand way. "It is possible that she [her sister] escaped. Maybe somebody out there will tell me what happened." Of nine children in her family, only she and her brother are known to be alive today, she said.

In addition, Allan A. Ryan Jr., the U.S. Justice Department's chief investigator of Nazi war criminals, is in Jerusalem this week. Ryan has asked participants to fill out a brief form describing their backgrounds, experiences and present addresses so that the Justice Department can contact them if they can be of help in presenting testimony against alleged Nazi war criminals in the United States. Despite their horrowing experiences the survivors who are gathering in Jerusalem appear to have found comfortable shelter far from the horrors of their youth. So it is altogether appropriate that the survivors village was dedicated yesterday with a traditional Jewish prayer that gives thanks to God, "who has kept us in life, and preserved us, and enabled us to reach this time."