The density of a substance is the mass of one unit volume. The density of silver is 10.5 g/cm^3. Each cm^3 of silver weighs 10.5 g at 20`^@` C.
Density = mass/volume
=> volume = mass/density
A piece of silver with a mass of 31.5 g has a volume given by:
volume = 31.5/10.5
=> volume = 3 cm^3
The required volume of the piece of silver is 3 cm^3.