The balanced chemical reaction is this:
3I2 + N2 --> 2NI3
3.58 g NI3 / 394.71 g/mol = 9.07x10^-3 moles NI3
Using the stiochiometric ratio from the reaction,
9.07x10^-3 moles NI3 (3 mol I2 / 2 mol NI3) = 0.0136 mol I2
In grams,
0.0136 mol I2 (253.80 g/mol) = 3.45 g I2