Complex sentence: Most of these migrants arrived and settled around Nisibis (Mtsbin), to the south of Armenia, and the extensive lands of the south became known, after their name, as Mygdonia.
Split into simpler sentences: Most of these migrants arrived and settled around Nisibis (Mtsbin), to the south of Armenia. The extensive lands of the south became known, after their name, as Mygdonia.