One molecule of the antibiotic known as penicillin g has a mass of 5.553×10−22g. what is the molar mass of penicillin g?

Molar mass means the mass of one mole of penicillin.

Now, one mole of penicillin contains 6.022 x 10^23 molecules (That's Avogadro's number).

Therefore:
molar mass of penicillin = mass of 6.022 x 10^23 molecules
molar mass of penicillin = mass of one molecule x 6.022 x 10^23
molar mass of penicillin = 5.553 x 10^-22 x 6.022 x 10^23
                                      = 334.40166 grams

It is 4.92 e-4 sorry if i am wrong