Adam Clarke on Acts 18:23

Went over all the country of Galatia and Phrygia - Both were provinces of Asia Minor: see on Act 2:10 (note).

In order - Καθεξης, A word peculiar to St. Luke; see his Gospel, Luk 1:3; Luk 8:1; and his history of the Acts, Act 3:24; Act 11:4, and the place above; the only places where this word occurs in the New Testament. It properly signifies, in order, distinctly, particularly; from κατα, according to, and ἑξη, order, as opposed to confusion, indistinctness, etc. If St. Paul went up to Jerusalem at this time, which we are left to infer, for Luke has not expressed it, (Act 18:22), it was his fourth journey thither; and this is generally supposed to have been the twenty-first year after his conversion. His first journey is mentioned Act 9:26; his second, Act 11:30; his third, Act 15:4; and his fourth, Act 18:22, the place above.