What is the easiest way to do mole conversions i. e. to grams, molecules, and formula units?

For mole conversion always remember 1 mole of compound = molar mass of compound.

Ex. 2 moles H20 to grams

2mol H2O x 18 g / 1mol H20

For molecules use Avogadro's number like moles multiplied to 6.022x10²³ answer will be in molecules.