What focal length lens would you need to make an enlargment from a 2 1/4 x 2 3/4 (6x7) negative?

90mm would do it, that is the standard lens on a 6x7 camera, or one of them. 90mm equates to about 43mm on a 35mm comparison and the standard lens for printing 35mm is either 45mm or 50-55mm.