Converting MP3 To Another format

[TorqueVR]

I dictate a lot of dictation that I email to my typist. I've been using a digital Olympus dictation machine for years but its packed up and I've bought a new one. However instead of the files being in an Olympus audio format like the old machine the new machine records them as MP3 and they are over twice the size and it's real bh emailing them.

How can I save the files in another format, and what format should I try to use?