What you can do, however, is simply have the file play and use a program that will capture the audio playing on the computer and encode that as an .mp3.
First, to open the .trm file you need to have a program that is capable of opening this file and playing it. I used ForTheRecord player, available free here. http://community.fortherecord.com/
You must first register at the site (free) to allow you to download the free software.
Then I tried several free audio capturing programs before I finally found one that not only worked, but was pretty easy to install and use... FreeCorder.
http://www.applian.com/sound-recorder/
Free corder actually installs as a tool bar on your internet explorer... not my favorite place to have it installed, but it works and the price is right... (free!).
Simply launch Internet Explorer and get your trm player ready. Then click the Record Audio button on the Freecorder bar in Internet Explorer to start the recording.
Now quickly hit play on your trm player. You will see Freecorder capturing and recording the audio.
When you are done capturing the audio, simply move the mouse over the Freecorder recording window and hit Stop Recording.
Once you hit Stop Recording your mp3 version of whatever audio you were playing will be saved to a folder name Freecorder in your My Documents folder. In my particular setup, two copies of the audio file were saved using different drivers. Just pick the one that sounds the best if this happens.
Now you know how to not only convert .trm files to .mp3, but virtually convert any type of audio to .mp3!