The number of water molecules in ^moles of water is calculated by use of Avogadro law constant
that is 1mole = 6.02 x10^23 molecules
what about 6moles
by cross multiplication
= {6moles x ( 6.02 x10^23)} /1mole = 3.612 x10^24 molecules
this is because moles and moles cancels each other