Question

the density of solid cu is 8.96 g/cm3 . How many atoms are present per cubic cenitermeter of Cu?

Answer 1

Convert the mass to moles
mol=g/Mr
Once you have done that you need to convert the mole value in the number of Atoms.
convert moles to atoms: by multiplying moles by avogadros constant

There are always 6.022 x 10²³ atoms in one mole of substance.

Answer 2

But first, convert density to mass using the relationship d=m/V