The original language of the New Testament was Greek. When Paul and others wrote about baptism, they always used a Greek word that meant to “dip or immerse.”
There are other Greek words that mean “to sprinkle or pour.” If the writers had intended to introduce other modes of baptism, they would have chosen the appropriate word. Instead, they specified immersion.
It is not necessary to translate Greek words to understand this. In Acts 8:38, Philip baptized a man from Ethiopia. After the man expressed his faith in Christ, Philip and the man went down into the water: an action not necessary if baptism were by sprinkling.
Immersion was the commonly accepted form of baptism in the church for hundreds of years. It was only in later centuries that man began to substitute different modes.