Find out what you've got.
I'd look closely at www.Graflex.org first to determine what you've got. If the camera was new in 1940, then it is an Anniversary Speed Graphic. They came in three sizes (2 1/4 x 3 1/4, 3 1/4 x 4 1/4 and 45 in.) and two different backs (Graphic and Graflex) all this will be explained on that site. Once you know what you have and if everything works including the lens, if it has a shutter, then I'd go to that popular auction site and do a search for that model using the completed auctions feature. There are lots and lots every week.