# What conversion factor do you use in converting number of moles into number of formula units?

Well, you use $\text{Avogadro's number}$, $6.022 \times {10}^{23} \cdot m o {l}^{-} 1. \ldots . .$
One mole of stuff, specifies $6.022 \times {10}^{23}$ individual items of that stuff. See this old answer and links.