The image shows the dimensions of the various framing pieces.

CUT LIST for 2x4s:

2 @ 4' - 8 1/2"

3 @ 3' - 6"

4 @ 3' - 3"

Since you are making two of these modules, make a second set of the pieces listed above.

Helpful note: write the length of the pieces on them! This way you know you are using the right pieces as you assemble the unit. The framing will all be buried under finish materials later, so you don't have to worry about marking up the boards.