Complex sentence: Ashoka's Yavanas are placed in Arachosia (Kandhahar) and his (western) Gandhharas are in Pushkalavati/Peshawar while the eastern Gandharas are in Taxila on east side of river Indus.
Split into simpler sentences: Ashoka's Yavanas are placed in Arachosia (Kandhahar) and his Gandhharas are in Pushkalavati/Peshawar. The eastern Gandharas are in Taxila on east side of river Indus.