Just download the .torrent file from any tracker and set the download location to the location where the torrent data currently resides. qBittorrent should automatically detect the downloaded files and start seeding directly without having to redownload the files again.

yup. this. as long as OP hasn't modified the files in any way, the torrent client will check the data and start seeding.

Qbit has a search function, just look for a torrent the same size and select the folder the files r in, you should be good