To reach the Ne configuration, each species gains/loses electrons: $\text{Na}\to {\text{Na}}^{+}$, $\text{F}\to {\text{F}}^{-}$, $\text{O}\to {\text{O}}^{2-}$, $\text{N}\to {\text{N}}^{3-}$.

All four ions are isoelectronic ($10$ electrons), so size is governed by $Z_{eff}$ — lower nuclear charge gives a larger ion.

Order of nuclear charge: ${\text{Na}}^{+}(11)>{\text{F}}^{-}(9)>{\text{O}}^{2-}(8)>{\text{N}}^{3-}(7)$.

So ${\text{N}}^{3-}$ is the largest.