Baptism is the initiation rite of the church. Throughout the Book of Acts baptism occurs immediately after belief. In no case does baptism occur before belief.
Just consider a couple examples.
Acts 2:41 says, “So then, those who had received his word were baptized; and that day there were added about three thousand souls.” The Scripture is clear, those who received the word were baptized.
Acts 8:21 says, “But when they believed Philip preaching the good news about the kingdom of God and the name of Jesus Christ, they were being baptized, men and women alike.” In this case, the Samaritan men and women who believed the gospel were baptized.
Acts 8:35-38 says, “Then Philip opened his mouth, and beginning from this Scripture he preached Jesus to him. [And 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.'] And he ordered the chariot to stop; and they both went down into the water, Philip as well as the eunuch, and he baptized him.” Once again, baptism follows belief.
Acts 16:14,15 says, “A woman named Lydia, from the city of Thyatira, a seller of purple fabrics, a worshiper of God, was listening; and the Lord opened her heart to respond to the things spoken by Paul. And when she and her household had been baptized, she urged us, saying, ‘If you have judged me to be faithful to the Lord, come into my house and stay.’ And she prevailed upon us.” The Lord opened her heart to respond to the gospel, then Lydia was baptized.
Later in Acts 16, the Philippian jailer was baptized after he believed. In Acts 18, Crispus and the Corinthians were also baptized after they believed.