Mark Allan Powell dates Paul's visit to Thessalonica to ca. 48-52.
Mark Allan Powell, Introduction the New Testament: A Historical, Literary, and Theological Survey, 2nd ed. (Grand Rapids, MI: Baker Publishing Group, 2018), 372
Paul's second missionary journey brought him to Thessalonica around 48-51. According to the book of Acts, he crossed over to Europe from what is now Western Turkey. He landed at Necropolis. . . and went first to Phillippi, where he managed to found the church to which he would later write his letter to the Phillippians (Acts 16:11-40).