The molar ratio of Li to N2 in the equation 6Li + N2 —> 2Li3N is:
6 moles Li / 1 mole N2
This is because this equation is balanced, and therefore the mole ratios exist just as they do in the reactants of the equation (there are 6 parts Li per each part N2 in order to create the product; this also holds true for moles).
Hope this helps!