It is not unusual to encounter individuals who do not have records of their baptisms for various reasons (natural disasters, war zones, misplaced records, poor record keeping, etc). In such situations the Church simply asks for two persons who were present at the baptism to sign statements attesting to the fact that the person in question was indeed baptized using the Trinitarian formula… This can be your parents, godparents, or whoever else was there. Your parish priest should have that paperwork.
If even that is impossible then you would most likely be what’s called “conditionally baptized.” It would be like a normal baptism except that the priest would say, “If you have not already been baptized then I baptize you in the name of the Father, Son, & Holy Spirit.”
