Can I convert mcdx files back to xmcd?

So, about a year ago my company allowed us to purchase Mathcad Prime and we converted all of our old Mathcad files over to that format.  Also, of course, all of our new files were made with prime.  Then, around 6 months ago, our company was bought out and now we only have Mathcad 15.  Is there a way that I can convert those files back to xmcd so that I can work with them again?