hello,

The atomic mass unit (u) is a unit that describes the masses of individual atoms and molecules. The atomic mass is the weighted average of the masses of all isotopes of an element. The molecular mass is the sum of the masses of the atoms in a molecule

Expression of molar mass is grams per mole. It can also be expressed as kilogram per mole. Molecular mass is expressed in atomic mass units.

also, note that,

It's easy to find the molecular mass of a compound with these steps:

Determine the molecular formula of the molecule. Use the periodic table to determine the atomic mass of each element in the molecule. Multiply each element's atomic mass by the number of atoms of that element in the molecule.

hope that helps