1 mole of any substance contains Avogadro's number of atoms.
Therefore, to know the number of atoms in 1.004 moles of Bismuth, all you have to do is multiply the given number of moles by Avogadro's number as follows:
number of atoms = 1.004 * 6.022 * 10^23 = 6.046088 * 10^23 atoms
