A rectangle prism is measured 84cm (L)X 42cm (w) X 56cm (H). What is the largest size cube that fits the dimensions of the prism? What number of cubes is required?

Question

i don't even know how to start it T_T

The question is poorly worded

Interpretation #1
The largest cube to fit into the box is obviously one which measures 42 by 42 by 42 and you can only get one in

Interpretation #2
What is the size of the largest cubes with which I can fill the box
the largest to fill the entire base is a 2 by 2 by 2.
I will let you figure out how many of those will fit in