With this it is unit cubes and volume

So hmm notice the picture below

let us check the volume of the larger prism
then we'll see the volume of the cube

then we'll simply divide the larger prism's volume by the cube's and that'd show how many of the cube's volumes can fit in that amount of volume then



now.. part B) hmmm looks a bit circular somewhat

the volume of the larger in terms of the cube.. well, is 180 cubes in it, each 1/64 in volume I gather is just 180 * 1/64 then

now...in terms of a "unit cube", meaning a small cube, with sides of 1 unit long

well, a cube of sides 1, is V = 1*1*1, so is V=1

hmmm in terms ..not sure I find that part very clear, sounds like its asking to see how many unit cubes in the large prism.... in which case you can simply do the same division 45/16 divided by 1