Switching names between files?

So I have the entire season of a particular TV show. In order for my media player to pick up the correct external subtitle files, they have to have the same name as the video.

So s01e01.mkv needs a file named s01e01.srt.

The problem is, all of my SRT files have the wrong name. What method do I use to get all the srt files to have the same name as the existing mkv files?

It's impossible to answer your question without more information.