The number of atoms = number of moles x Avogadro’s number (6.022x10^23)
So first you need to find the number of moles of carbon 12
Number of moles = mass (g)/ molar mass
n= 6/12
= 0.5
Then put that into the equation for number of atoms so
Number of atoms = 0.5 x 6.022 x 10^23
= 3.011x10^23
I’m not 100% sure if that’s correct though