The Bible can't be used in this way. This is where division and confusion comes from in the body of Christ. First read the whole context of these verses. Then take all the verses on salvation and you'll know the answer. Every verse, as Isaiah said, has a mate(Isa 34:16) what's these verses mate? Verses are always a chorus, they don't like solos. Finishing reading and group them with others. Get the full meal benefit.
THE JAILER
They replied, “Believe in the Lord Jesus and you will be saved, along with everyone in your household.” [SUP] [/SUP]And they shared the word of the Lord with him and with all who lived in his household. Even at that hour of the night, the jailer cared for them and washed their wounds. Then he and everyone in his household were immediately baptized (Acts 16:31-33)
SIMION
But now the people believed Philip’s message of Good News concerning the Kingdom of God and the name of Jesus Christ. As a result, many men and women were baptized.... Then Simon himself believed and was baptized. (Acts 8:12-13)
PETECOST
Peter’s words pierced their hearts, and they said to him and to the other apostles, “Brothers, what should we do to be saved?”[SUP] [/SUP]Peter replied, “Each of you must repent of your sins and turn to God, and be baptized in the name of Jesus Christ for the forgiveness of your sins... (Acts 2:38)
JESUS SAYS
Anyone who believes and is baptized will be saved.(Mk 16:16)
“I assure you, no one can enter the Kingdom of God without being born of water and the Spirit."(Jn 3:5)
The apostles would follow these commands, along with the great commission.
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Salvation is more than just believing, James writes in 2:19 "the demons also believe and shudder!"
According to the Bible in completion to be saved steps:
1. Confessing Jesus as the ultimate authority of your life (Rom 10:9)
2. Pisteuo, meaning to have faith, to trust in; the fact that God raised Jesus from the dead (Rom 10:10)
3. Metanioa, meaning to have a complete change of mind, character, person (Acts 2:38). This can happen before, during, or after baptism(Acts 10:47, Acts 8:17, Acts in general)
4. Be baptized immediately in the authority of Jesus (Acts 16:33, Acts 2:38)
5. Receive the Holy Spirit inside of you (Acts 2:38, Jn 3:5)
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That's the way of salvation, but not the end. You must die to yourself daily(Mt 16:24) by cutting off sin (Col 3:5,Deut 30:6) with the power of Holy Spirit (Rom 2:29), and do good works in which we were created for(Eph 2:10) to glorify God(Mt 5:16). Think that about sums it up

There is a lot of OT fulfillment in salvation and is what makes the steps important, all of them. God doesn't change and what the NT is, is the fulfillment of the OT. OT wasn't made void but brought to it's fullness because of Jesus.