You need to give more explanations on what exactly you want to do:
- Do you want to have text files just to read those from the project, without any modification ?
Then, use File.DirAssets and read them from there when you need them.
- If you need text files to read but you want to make modifications, but only for your project ?
Then use File.DirInternal. You need to check if these files don't exist in File.DirInternal, if no, you need to copy them from File.DirAssets to File.DirInternal.
- If you need text files accessible from outsides your application.
Then use rp.GetSafeDirDefaultExternal, and copy them if they don't exist.