We know the formula of the density:
ρ =

;
So the mass will be equal to:
m = ρ * V = 2.70 * 21.3 = 57,51 g =
57510 mg of substance.
So the answer is 57510.
Get an equal amount of each element by adding coefficients to the different compounds.
The molar mass of Fe would be 55.8450.