Skip ingame resource download by already keeping the files on the Android device
Solution 1:
The folder you're looking for is called "Android" and is in your internal storage. Android apps put their files in either "data" or "obb" folders inside the Android folder.
So
/Android/data/
and
/Android/obb/
Then inside those folders there is a folder for each app. The folder will have the same package name as the application. For instance the package name for Real Racing 3 is com.ea.games.r3_row and can be seen in the url in the app store: https://play.google.com/store/apps/details?id=com.ea.games.r3_row&hl=en
I believe it's possible you might have files for the same app in both folders, but don't quote me one this.
This means that the Real Racing 3 files will be in either
/Android/data/com.ea.games.r3_row/
and/or
/Android/obb/com.ea.games.r3_row/
You can use apps to associate a package name with an app.
Also I believe there are backup apps out there that CAN backup those files for you, but I've never needed this o I haven't looked for any.