Paul’s First Missionary Journey
Paul’s first missionary journey is found in Acts 13 and 14. Paul and Barnabas set sail with John as their helper from about 46 to 48 A.D. and their first stop was Cyprus. Acts 13 records that they made it to Salamis in Cyprus, and proclaimed the word of God in the Jewish Synagogues.
As they traveled through the whole island they came to Paphos where they ran into a Jewish sorcerer and false prophet named Bar-Jesus who was an attendant to the proconsul. Paul and Barnabas were actually summoned by the proconsul because he wanted to hear more about Jesus.

 
But when they arrived, the false prophet sought to turn the proconsul away from the truth, but the Holy Spirit came upon Paul who then rebuked the man and caused him to be blind. It was because of this that the proconsul saw the power of God and converted.
After they left Cyprus, they made their way to Perga in Pamphylia where John left them to go back to Jerusalem. They went from there to Pisidian Antioch.
In Pisidian Antioch, they went to the synagogue and began preaching; many received them and what they taught and urged them to continue on, even following them in order to learn more. But they were removed from the city after the jealousy of the Jews rose up and they stirred up the God-fearing women and leading men of the city and persecution broke out against Paul and Barnabas.
They then traveled to Iconium and taught in the Jewish Synagogue where a great number of Jews and Gentiles converted to the faith. But again, other Jews stirred up trouble for the two missionaries. They left sometime after arriving because a plot against their lives arose.
Next was Lystra and Derbe where the Galatian church was planted. While they were there they got mistaken for gods. After Paul healed a crippled man, the city erupted, claiming that Barnabas was Zeus and Paul was Hermes. This greatly distressed both of them, so they went out into the masses to set the record straight and tell them the Gospel message, but as they were doing this, the crowds were won over by Jews trying to cause trouble for Paul and Barnabas. As a result, Paul was stoned, almost to death. The very next day he and Barnabas went to Derbe.

Upon arriving in Antioch, they called the church together and reported everything God had done through them and how he had opened the door of faith to the Gentiles, too. And they stayed there with the believers for a long time.
Acts 14:27-28

After a time of preaching in Derbe, they returned to Lystra, Iconium, and Attalia, then they returned to the church in Antioch where they first set sail from and spent some time there before heading out a second time.
During his missionary journeys, Paul wrote multiple letters that became known as the epistles. And during Paul’s first missionary journey he wrote a letter to the church in Galatia which was his first epistle and is known as the book of Galatians in the Bible.
He wrote to encourage the Galatians and bring truth to them because they were being choked out by a false understanding of the Gospel that taught that you needed Christ plus the Law to be saved.
Source: https://bethanygu.edu/news/missionary-journey/