How do I solve this problem? Esimating the number of atoms?

How do I solve this problem? Esimating the number of atoms?

Estimate the number of atoms in 8.651 g of iron using the mass of an atomic mass unit (). The atomic mass of Fe is 55.85 u.

Additional Details

I know the atomic mass unit is 1u=1.661x10^-27kg. But I don't know what to do with that. First we convert grams of iron to Moles of iron. One Mole of anything contains its atomic mass unit grams of that material. In this case, one mole of iron contain 55.85 grams of iron.

So, 8.651g Fe*(1 mol Fe/55.85g Fe) = 0.155 mol Fe.

Now, we convert moles to atoms. One mole of an element contains 6.022x10^23 (Avogadro's Number) atoms of that element.

Thus, 0.155 mol Fe* (6.022x10^23 atoms Fe/mol Fe) = 9.33 x 10^22 atoms of Fe.

Don't lose sight of the g-atoms because of the atoms.
The weight of Avogadro's number of iron atoms is 55.85 g.
So we have a simple proportion:
8.651 g/55.85 g = # of atoms in problem/Avagadro's #

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