Via PTC support
If you have any legacy worksheets (PTC Mathcad 15.0 and earlier versions) that you want to convert to PTC Mathcad Prime 3.1, please read the Migration Guide found in the References dropdown under the Resources tab.
It is important to realize that the worksheet conversion utility is found in PTC Mathcad 15.0 M010 or later, so you will need to download and install this version of PTC Mathcad as well.