To convert the formula unit to mass, we need to divide the given formula units by Avogadro's number, 6.022 x 10^23 and we get the mole of beryllium nitrate. To convert to mass, we need to multiply the number of moles with the molecular formula of the compound which is 133.022 g/mol.The answer is 0.006185 g or 6.185 mg.