Unfortunately Prime can't read older Mathcad files on its own. The files have to be converted to the new format. You may have noticed the appropriate menu in the ribbon or the link to the stand alone converter in your program collection.
For the converter to work you must have a current version of mathcad 15 installed on your machine. If you have a license for Prime the same license is valid for Mathcad 15, too. You can download Mathcad 15 here: Thank You for Your Interest in PTC Mathcad 15 | PTC
You may stop after installing MC15 and keep working with that version as Prime 2 sure is a software you really should ban from your computer. Its not worth working with as its an inferior version. Prime 3 may be a very little bit advanced but still lacks a a lot of features and can not live up up to MC15.
If you insist on converting your library to Prime format you have to be aware that unless you have rather basic functions in your sheet, the converted sheet may not work at all or will at least need a lot of hand tuning. Also older versions of Mathcad are more capable and support more featiures so a lot of things simply cannot be convverted as there is no equivalent in Prime.
Good luck anyway
Werner
EDIT: I am not sure how far back Mathcad 15 can read older files.
The files you attached seems to stem from the DOS 2.5 version of Mathcad and I thought that Mathcad 15 should be able to read those files. But I just tried and my Mathcad 15 seems to have troubles readibg that file.
