So you would need to find the volume of both the smaller box and larger box. To find the volume of a rectangular prism you multiply the length x height x width.
Smaller rectangular prism:
4 x 2 x 4 = 32
Larger rectangular prism:
6 x 6 x 2 = 72
Then add them together so 32 + 72 = 104
Answer: 104cm^3
Hope this helps! :)