A cube with side length of 2cm has the following volume:
[tex] 2\cdot 2\cdot 2 = 8[/tex] cubic centimeters.
A box with side length of 4cm has the following volume:
[tex] 4\cdot 4\cdot 4 = 64[/tex] cubic centimeters.
So, you can fit
[tex]\dfrac{64}{8} = 8[/tex]
ice cubes in the box.