If you have left the downloaded data in the same place (directory and/or drive) and use µTorrent, you could copy the content of %AppData%/utorrent from your old installation to the new.
The other way is the reseed procedure:
For µTorrent/BitTorrent look there > https://forum.gaytorrent.ru/index.php?topic=6539.0
or generally:
https://www.gaytorrent.ru/faq.php?lan=1#505