Answer
See answer below.
Work Step by Step
$\begin{array}{|l|cc|}
& Mg^{2+} & Fe^{3+} \\
\hline
PO_4^{3-} &Mg_3(PO_4)_2 - Magnesium\ phosphate & FePO_4 - Iron\ (III)\ phosphate\\
NO_3^- &Mg(NO_3)_2 - Magnesium\ nitrate & Fe(NO_3)_3 - Iron\ (III)\ nitrate
\end{array}$