so we are doing molecular conversions in chemistry and there is one thing i need guidance on?

we are calculationg the mass in grams of 4.55x10^25 molecules of manganese(III)phosphide. After converting to molecules to mols, and mols to grams, my teacher said that the mass of manganese(III)phosphide is 85.91g for 1 mol. she did not multiply the mass of the manganese by 3. Am i wrong or is she right? in that equation, are you supposed to multiply the Ma by 3 or the P by any number? pls help me... thanks