To solve for density the equation is density= mass/volume. To find mass you would need to change the equation to mass = density x volume.
An example according to socratic.org would be:
The density of copper is 8.933 g/cm3. What is the mass of a sample of copper with a volume of 10.00 cm3?
MassCu = 8.933g1cm3 x 10.00 cm3 = 89.33 g