to find volume, multiply length x width x height.
4 1/2 x 5 x 3 1/4
4.5 x 5 x 3.25 = 73.125
1/4 = 0.25
Divide the total of the large cube to the small cube.
73.125/0.25 = 292.5
292 and 1/2 of the small cube(s) are needed to fill the right rectangular prism.
hope this helps