How many grams are there in 3.30x10 23 grams of n2i6

Technically, the answer should be 3.30 * 10^23 grams. But I think you mean either molecules, atoms, moles or grams of Ni2I6 with that number of molecules .

1 mole of Ni2 I6  = 6.02 * 10^23 molecules
x  [mole] = 3.30 * 10^23 molecules

1/x = 6.02 * 10^23 / 3.30 * 10^23 Cancel the 10^23 on the right side
1/x = 6.02 / 3.30 Cross multiply
3.30 = 6.02 x Divide by 6.02
3.30 / 6.02 = x 
x = 0.548 moles 

what to do from here?

1 mole of Ni2I6 is
2 * Ni = 2 * 59 = 118 grams
6 *  I = 6 * 131 = 786 grams
Total  =               904 grams

Set up a proportion.
1 mole Ni2I6   = 904 grams  
0.548 moles    = x

1/0.548 = 904/x Cross multiply
x = 0.548 * 904
x = 495.4 grams of Ni2I6 <<<<<< Answer.