John Gill Commentary 2 Kings 10:33

"from the Jordan eastward, all the land of Gilead, the Gadites, and the Reubenites, and the Manassites, from Aroer, which is by the valley of the Arnon, even Gilead and Bashan." — 2 Kings 10:33 (ASV)

From Jordan eastward
This was principally the coast on which Hazael smote them, to the east of the land of Canaan:

all the land of Gilead, the Gadites, and the Reubenites, and the
Moabites ;
the country on the other side Jordan, given to these tribes by Moses, at their request, which were before the kingdoms of Sihon and of Og:

from Aroer, which is by the river Arnon, even Gilead and Bashan :
countries which the Israelites first conquered, and were the first they lost.