The total mass of the original tissue were from the source which are the pig ovaries. But first, convert 5.6 tons to mg.
5.6 tons × (1000 kg/1 ton) × (1000 g/1kg)×(1000 mg/1g) = 5.6 x 10^9 mg
Thus, the percentage of estrone in the original tissue is
(12.0 mg /5.6 x 10^-9 mg) x 100 = 2.14 x 10^-7 %