How many nitrates are in 3Pb(NO3)2

I thought it was 2 NO3's, and then 3 more, resulting in 5 NO3's. My friend told me it was 6 because it's 2 NO3's, then multiplied by 3.

Coefficients in chemical equations are multiplicative.

1 Pb(NO3)2 molecule has 2 nitrate molecules.
3 Pb(NO3)2 molecules have 6 nitrate molecules.

Your friend is correct, NO3 is a nitrate so mutiple that by 2 to get 2 nitrates. Then you see the 3 infront of Pb? That applies to the whole equation, so multiply everything in the equation, (including No3) by 3 to equal 6.

The answer is 6.
There are 2 NO3's in each Pb(NO3)2 (lead(II) nitrate).
And in this particular case, there are 3 lead(II) nitrates.
You can set up a proportion-- [2NO3:1Pb(NO3)2 = XNO3:3Pb(NO3)2].
Then cross-multiply.