How do I solve these two problems ?

1.The mass of a quantity of is 32.7 g. What is it's volume in cm raised to the third power ?
2.The volume of a quantity of water is 0.42 cm raised to the third power. Find its mass in g.

1. You would need to know its density to calculate the volume. Mass alone is not enough.

Did you omit the words "of water" in the qustion? If so, the density is 1.00 g/cm^3

2. 0.42 cm^3 of water has a mass of 0.42 g