Molar mass  is the mass in grams of one mole of molecules or formula units of an element or a compound.
The number of the molar mass you can find the Periodic Table of Elements (PTE): It is the number in superscript in front of each element symbol:

* 1 mol hydrogen atoms (H) weigh 1.0 g, 1 mol helium atoms (He) weigh 4.0 g, .....
As molecules as well as lattices of elements and compounds are formed by reaction of atoms, the mass of 1 mol of them can easily be calculated:
* 1 mol hydrogen molecules   (H2): 1.0 + 1.0 g                =      2.0 g
* 1 mol watser molecules     (H2O): 1.0 + 1.0 + 16.0g     =    18.0 g
* 1 mol sulfur molecules         (S8):  8 x 32.1 g                =  256.8 g
* 1 mol sodium chloride (NaCl): 23.0 + 35.5 g               =   58.5 g