In 1 molecule of C6H6 is 6 atoms of carbon, yes?
From the definition of mole, we know that 1 mole of molecule (for example C6H6) contains 6,02x1023 molecules of C6H6. If one molecule of benzene is built by 6 atoms of carbons, so 6,02x1023 molecules of benzene are built by 6x6,02x1023 atoms of carbons.
You must do analogous caluculation. Good luck.