How to convert a tmx file to an XLIFF file

Hello,
I am trying to find out how to convert a tmx file to an XLIFF file. My tmx file is from Trados Freelance Studio 7. I have other versions, but still prefer the old platform to others.

I am thinking that the tmx file is pretty much the same as an XLIFF file, or that the unclean BAK file might be, but my client wants an XLIFF file.

I would really appreciate any help you can give me!!

Thanks!

Laura