Triangle DEF has been dilated to form triangle D'E'F. What is the least amount of information needed to determine if the two triangles are similar?

I think the missing part of the box volume is 12 inches and the volume of the box is 84 inches in total. 
Here's how I got it.

First, I multiply 6 by 4 for the base and then multiply the answer, 24 by 3 to get 72 inches.

Next, I need to find the other small box on top of the it. So then I multiply the width, which is 1.5 feet by the length( up and down ) which is 2 because I subtracted the other lengths( up and down ), 8 by 6.

Finally, if you multiply them together, you'll get 3 because 1.5 x 2 = 3. 
To find out what to multiply them by you need to find the height which is 4 inches ( it's on the bottom already. ) 

3 x 4 = 12. 12 + 72 = 84

So, the volume is 84.  ;)