What novena should i pray for this?

there's a guy i use to no he was my brothers friend and he was adopted and he was never happy about being adopted his real parents are in jail and we moved out of that neighborhood and i had not seen him for a wil but i slow him the other day and i can tell he is on drugs and he is running wiled i really want to help him so i am going to pray a novena but witch one should i pray and for how long