Manually updated, changed database prefix ERROR

My website was recently attacked by hackers.
The hosting company took the website offline and I had to delete some files and update WordPress manually in order for the website to be online again.

I did that, but when uploading wp-config.php again, I accidentally changed the table prefix and installed a new WordPress site on the root.
The old website, plugins, content and theme are all gone..
The weird thing is: I can still see the old theme on FTP. In the correct folder even.
Also, on phpmyadmin I can see the old tables.

Please help me fix this huge problem, because I have no idea what to do!

Thanks in advance for any help.