For most of my shows, I already have their subtitles(downloaded manually) bearing the exact same filename as their episodes as should be the case.

Now I have also started using Plex just 2 days ago and I have noticed that it shows those subtitles as Unknown language and I discovered it is because my subtitles do not have a language identifier in their names. Now all I want to do is rename only the subtitles with adding their language code but when I use the sample naming scheme
{n} - {s00e00} - {t}{'.'+lang}
the application shows an error

For now, my shows look like this

How do I rectify this error/solve this requirement of the media file? Also, when I rename other tv shows, with both their video files and subtitles, how do I write a scheme which renames videos to their intended name and renames subtitles with their language code or do I have to rename them separately?
How do I integrate FileBot to BitTorrent?