How many moles of atoms are in 2.00 g of 13c?

I think what '13C' means is the isotope of carbon with mass number of 13. Its mass is 13 amu. The unit amu is equivalent to g/mol. The average atomic mass of Carbon is actually 12. But since we are solving for this particular isotope, we use a molar mass of 13 g/mol.

2 g C-13 * 1 mol/13 g = 0.154 moles of C-13