missing userdata.json file

After watching couple of apk editor pro mod videos I learned that games have a file named userdata.json in assets folder but I couldn't find it on the game's files and I thought It might be named different but there were so many .json files so I was wondering how could I find that file?
Note: I'm totally amateur I have no idea about modding just wanted to try for a game I like
game I tried modding: Omniheroes