Do I need to convert to Catholisim?

Your baptism is valid, but you need to be confirmed. Check with your diocese and join a good RCIA cl. You will formally learn the faith and be confirmed the next time Catechumens are received. In my diocese, it is usually in December and at the Easter Vigil M. I was baptized Baptist and was confirmed in 2000. Your Catholic baptism will make it easier for you. God bless your grandmother for keeping you in the faith! Study diligently and receive our Lord often in the Eucharist. There is no love affair equal to the one between you and the Catholic faith. I will pray for you!