I used a calculator to get this answer: cubic feet.
You might want to see a couple of the pages on my own website that pertain to perimeters, areas, and volumes. Go to "www2.seminolestate.edu/rrapalje". Near the bottom of my Homepage, look for "Topics from Geometry."
I think you will find the explanations easier to understand than traditional textbooks. My own students did!!
Dr. Robert J. Rapalje, Retired
Seminole State College of Florida
Altamonte Springs Campus