How do i go from molecules to moles? for example 1.50e23 molecules nh3 how many moles are in this problem?

To go from molecules to moles divide by Avogadro's number [6.02x10^23]
Example:
1.50x10^23 divided by 6.02x10^23 = 0.249 moles rounded to three significant figures

16- counting by fours