M. S. Ginn and Co., Washington's largest office supply and service firm, will close a $3 million deal tomorrow to purchase a warehouse of nearly 250,000 square feet in Prince George's County.

Located in Hyattsville, the warehouse will be purchased from L.S. Good and Co., former owners of the old Kann's Department Store, which had used the warehouse until Kann's went out of business 3 years ago.

Ginn Chairman Marsh Marshall said his company needs additional space to handle a sales growth of 15 percent a year. Ginn's sales for the year ended June 30 exceeded $39 million, he said, up from $35 million last year.

Ginns will remodel the warehouse to house operations it now has in four locations: office space in downtown Washington, manufacturing facilities in Bladensburg, Md., distribution facilities in another location in Bladensburg and mail-order operations in Richmond.

Marshall said the purchase, financed by loans from two area banks and a savings and loan, would not have been possible without the assistance of the Maryland Industrial Development Financing Authority.

Ginns also plans to move its office furniture showroom next spring from 1210 18th St. NW to 19th and L, where it will occupy the entire second floor and an 800 square-foot entry foyer on the first floor. Marshall said rising prices for the first floor space in downtown have forces Ginns to move its showrooms to the second floor, for which rents are cheaper.