I think you're a little confused over exactly what torrent files are, dear lady. They're simply text files that link computers around the world to the specific file that it is you're attempting to download.
I'm afraid you can't actually convert torrent files to .mp3. You can, though, download .mp3 files in this way ... though you won't be able to do it on public computers, such as in a library, at school, or at many places of work. The network security administrator would put a block on downloading this type of file as this is one of the quickest ways of getting your computer attacked by viruses, trojans, adware, and other types of malware.