Albert Barnes on Acts 23:34

Of what province he was. Greek, Of what heparchy επαρχιας he was. He knew from the letter of Lysias that he was a Roman, but he was not informed of what place or province he was. This he doubtless did in order to ascertain whether he properly belonged to his jurisdiction. Roman provinces were districts of country which were entrusted to the jurisdiction of procurators. How far the jurisdiction of Felix extended is not certainly known. It appears, however, that it included Cilicia.

Was of Cilicia. Tarsus, the birthplace of Paul, was in this province, Acts 21:39.

(f) "Cilicia" Acts 21:39