>>663456
> I was baptized at birth
If you were baptized with the Trinitarian formula (that is, in the name of the Father, the Son, and the Holy Spirit) there is no need for you to be baptized again. Catholics, Orthodox and almost all Protestants use this formula so you'll be fine
Have you been confirmed into the Catholic church? If not, speak to your priest about RCIA.
If you have, you will need to make a confession to enter into a state of grace to receive Communion
https://www.catholic.org/prayers/confession.php
The sins you confess will be the ones since your last confession, and if you can't remember, you will need to examine your conscience fully as suggested in the link.
God bless OP