Question 100170
To compute volume you multiple length by width by depth (or height, as the case may be). BUT, all of the values must have the same units of measure.

Here you have 42" for one dimension. The other two dimensions are in feet:  6 feet and 3 feet.

So, you have to convert 42" to feet, or 6 feet and 3 feet to inches, before you multiply.

Dividing 42" by 12" per foot, you get 3.5 feet. So the volume is simply 3.5 times 3 times 6 cubic feet.