The question of whether or not to pursue confirmation isn't a light one that should be put to strangers on an Internet forum.
Being Orthodox, we have some major differences with Catholicism, and so if you were someone I knew, right here with me, I would suggest you take some time, I'd introduce you to our priest, and try to help along the way.
But if you decide to pursue Confirmation in the Catholic Church, that needs to be something you discuss with a Catholic priest. I don't know what the requirements are, but it's not a light step to take. I think you should be at least somewhat purposeful. The Sacraments make this a more important decision than a Methodist person who wakes up one day and decides to go to a Nazarene church.
And while we teach full immersion (triple immersion in fact) in the name of the Father, Son, and Holy Spirit, we also recognize that a baptism done in the name of the Trinity is a baptism. In the Didache, which is an early writing of how the Apostles taught certain things to do in the Church, iirc, it talks about baptism preferred to be immersion, but if that's not possible, pouring will do. The water should be "living" ... i.e. moving and not stagnant, but if that nit possible, still water will do. It even says if there is no water available, one can be baptized with sand, if it's the only option.
So I don't think you need to be re-baptized. But learning the details of faith and making decisions going forward is a very good thing.
And even if you are not in a position to sacramentally Confess, talking with a priest can help.
God be with you!