The amount of charge in F (Faraday) required to obtain one mole of...

${Fe}_{3}{O}_{4}$ is a mixed oxide($\overset{+ 2}{Fe}O . \overset{+ 3}{Fe}2{O}_{3}$)

The net change in oxidation can be calculated as follows,

${Fe}_{3}{O}_{4}\overset{+ 8{e}^{-}}{⟶}3Fe$

For 3 moles of formation of iron, 8 moles of electrons are involved.

One mole of electrons charge is called one Faraday.

Charge for $1$ mole $Fe = \dfrac{8}{3}F$

$= 2 . 67F$