Read the account of the conversion of the Ethiopian eunuch in Acts 8. He confessed his belief but was still in need of baptism. Notice in Philip's preaching Christ to him and his inquiry regarding baptism. Obviously, part of Philip's preaching of the gospel to him included the need to be baptized as well as confession of belief per Romans 10:9
Acts 8:35 - Then Philip opened his mouth, and beginning at this Scripture, preached Jesus to him. 36 Now as they went down the road, they came to some water. And the eunuch said, “See, here is water. What hinders me from being baptized?” 37 Then Philip said,
“If you believe with all your heart, you may.” And he answered and said,
“I believe that Jesus Christ is the Son of God.” Water baptism "follows" conversion. (Acts 10:43-47)
Compare with John 20:31 - but these are written that you may
believe that Jesus is the Christ, the Son of God, and that
believing you may have life in His name. *What happened to baptism? *Also, what happened to baptism in (John 3:15,16,18; 5:24; 6:29.40.47; 11:25,26?) Did Jesus forget to mention it?
Confessing with our mouth that Jesus is Lord and believing in our heart that God raised Him from the dead are
not two separate steps to salvation but are chronologically together.
Romans 10:8 - But what does it say?
"The word is near you, in your mouth and in your heart" (TOGETHER) that is, the
word of faith which we are preaching, (notice the reverse order from verse 9-10) - that if you confess with your mouth that Jesus is Lord, and believe in your heart that God raised Him from the dead, you will be saved; 10 for with the heart one believes unto righteousness, and with the mouth confession is made unto salvation.
Confess/believe; believe/confess.
1 Corinthians 12:3 - Therefore I make known to you that no one speaking by the Spirit of God calls Jesus accursed, and
no one can say that Jesus is Lord except BY the Holy Spirit. There is divine influence or direct operation of the Holy Spirit in the heart of a person when confessing Jesus as Lord. This confession is not just a simple acknowledgment that Jesus is the Lord (even the demons believe that), but is a deep, personal conviction from the heart that Jesus is that person's Lord and Savior.