Append track number to beginning of filename

I've looked on the FAQ and searched but I can't figure out how to just add the track number to the beginning of the filename, but Not renaming it. So I want to add something to the beginning of the filename, but keep the rest of the filename intact. How do I do that? Everything I've tried completely replaces the filename.

It would have been so nice if you had told us what you have tried so far.

Try Convert>Tag-Filename
Format string: $num(%track%,2)_ %_filename%

That worked perfectly, thank you so much!
I'm sorry, I should have said what I tried. I searched for awhile on here and google, but no one seemed to have this specific problem. The few topics I found all pointed to "Action type: Format value Field: COMMENT Format string: %comment% xyz" so I tried using that. The other topics were about adding a word to the end of filenames, but that wasn't what I was looking for. Danke sehr!