You have 0.00809 moles of nitrogen in that much nitrous oxide.
First, look at the molecular formula of nitrous oxide,
So, to determine how many moles of nitrogen you have, you must first determine how many moles of nitrous oxide you have. To do that, use the compound's molar mass
This means that you get
Rounded to three sig figs, the number of sig figs given for .178 g, the answer will be