Explanation:
I assume you mean as second question "what is the volume of a cube with the surface area of 54 cm² ?".
first question :
volume is 8 cm³
the volume of a cube is side³.
8 cm³ = side³
side = cubic root(8) = 2 cm
add-on : the surface of a cube (6 sides) is 6 times the area of side² squares.
surface = 6 × 2² = 6 × 4 = 24 cm²
second question :
54 cm² = 6 × side²
9 = side²
side = sqrt(9) = 3 cm
and the volume would be
side³ = 3³ = 27 cm³