1)
Where in Mizrach were they?
1.
Radak: They were east of Gil'ad, for their entire land was east of Eretz Yisrael - Ever ha'Yarden Mizrachah. They spread east of Gil'ad, until Levo Midbarah.
2)
Why does it say "l'Min ha'Nahar Pras"?
1.
Radak: It means until Nehar Pras, and from Nehar Pras is Eretz Yisrael's eastern border - "Min ha'Nahar Nehar Pras Ad ha'Yam ha'Acharon Yihyeh Gevulchem."
3)
Why does it say "Ki Mikneihem Rabu"?
1.
Radak: This is why they needed to spread, for their flocks increased.
