To do this, we find the moles of each element. We get around 0.155 moles of Fe, 0.051 moles of P, and 0.206 moles of O. We then divide each one by the smallest one (which is 0.051 moles of P). We then get 3 for Fe, 1 for P, and 4 for O. This correlates to the empirical formula of the compound.