What does decompose a cube mean?

Let n > 1 for an n x n x n cube for the purpose of decomposing the n x n x n cube into unit cubes (1 x 1 x 1). For the above scenario we see that decomposing an n x n x n cube into unit cubes can be thought of dividing an n x n x n cube into unit cubes. When n = 2 we get 8 unit cubes after decomposing. When n = 3 we get 27 unit cubes after decomposing.

If necessary to further your understanding I would suggest drawing a picture of a 2 x 2 x 2 cube then divide each of the six-faces by 2 both horizontally and vertically. Then draw a 3 x 3 x 3 cube and then divide each of its six-faces by 3 both horizontally and vertically. Then count the number of unit cubes for both drawings. Again, when n = 2 you should count 8 unit cubes and when n = 3 you should count 27 unit cubes.