Great, that's the definition I was taught, as well. So, you want the concentration, presumably in Molarity?, of NaI. That's a given in this question, so that's done. Did you mix up questions? Not to be unnecessarily critical, but you, Frederick95,
et al tend to do this a lot, change questions mid-thread, and leave us to debate our own postings, with ourselves.
Does it mean moles? If so, if you're given molarity and volume, can you compute moles? Generally, n, means moles, for at least some formulas. You appear to have memorized a separate formula for n, I think you'd be better off understanding the Molarity=moles / L, and rearrange that one, whenever you're given any two, and asked for the third. You'll have enough to do, with trying to determine what you've really been given, and what you're really asked, as in this case.