how do i calculate the volume of a unit cell and volume of atoms within a unit cell for FCC and BCC

Answer 1

What do you have available? You can get at this two or three ways. Do you know the side, a, for them?
Then volume of unit cell = a³ for both BCC and FCC.

For volume of atoms, look up the formula for volume of a sphere. I think it's (4/3)*pi*r³. For BCC, multiply that by 2 because there are two atoms per unit cell. For the FCC, multiply by 4 because there are four atoms per unit cell.