How many oxygen atoms are contained in 4.39 grams of Al2(SO4)3?

The average distance between two molecules is 6.55 x 10 19 pm. What is this distance in nanometers? Report your number in scientific notation and with the correct number of significant figures. For example 1000 would be reported as 1.00e+3 and 0.001 would be 1.00e-3.