Mole to gram Stoichiometry

Are you just trying to balance the equation?

Pb(NO3)2 + KI → PbI2  KNO3       Need two I atoms   so add 2 to the left side  

Pb( NO3)2 + 2  KI → PbI2  KNO3       Now we need to balance the right side since we added 2 KI add 2 K to Right side 

Pb(NO3)2 +  2 KI → PbI2   2 KNO3        Now it is 'balanced'    One Pb on both sides, two K's , two NO3's , two I's

Go to this page and see lots of details on the reaction:

https://www.wolframalpha.com/input/?i=Convert+from+moles+to+grams+++Pb%28NO3%292+%2B+KI+%E2%86%92+PbI2+%2B+KNO3