The volume of the prism=volume of cube
l*b*h=16(1*1*1) , since it is a unit cube
l*b*h= 16, number of possibilities for 16 are 16*1*1,2*8*1,4*4*1,2*2*4.
Please do not take fractions into consideration because it is a unit cube only integer values will be accepted for l,b and h.
So, total 4 possibilities.