Buy the current version from the Play Store. Then, if you need the 2.10 OBB for modding (and you own a license), you can extract it using apps like “APK Editor” from your own backup – provided you never share it.
If it's zipped, extract it to find a folder named com.rockstargames.gtasa . Phase 3: Move to the Correct Directory obb gta san andreas 2.10
Even with correct installation, you may encounter some typical problems. Here are their solutions: Buy the current version from the Play Store