Volume is Length x width x height
1 box = 4.5 x 2 x 4 = 36
Each box is 36 cubic feet. Now divide the closet size by box size
185 cubic feet/36 cubic feet per box = 5.138
Since you can't have .138 of a box, and rounding up to 6 boxes is too much, the closet will hold 5 boxes (with .138 cubic feet left over).