Fetching previous saved database file after reinstalling the app.

I am new to ios development so please pardon if I am asking a silly question.

I need to check if my sql file from the previous installation of the same app exists in the device directory already. If yes, then I need to fetch that file instead of making the new one. But the bundle folder of the app changes after reinstalling the app. So I cant guess the name of the previously installed app bundle folder. I tried to save it elsewhere on the device, but it isn't allowing me. Please suggest me the solution.