Hi @ali11aziz! Hope you’re doing great and thanks for your post.
Upgrading your Dropbox account only provides an extended version history window from the moment of the upgrade onwards and not retroactively. So, if the file(s) were deleted more than 30 days ago, it may not be possible to recover them (based on the version history offered on the free Basic plan).
However, have you made sure to check your Deleted files and Events pages, just in case? If yes, please also check your Shared tab, as an extra step, and see if you can re-add the files from there.
Finally, are your colleagues also on a free Basic account?
Let me know what you find.