Older Word versions used to support every version of Wordperfect ever, even Wordperfect Mac which must have sold about 3 copies decades ago. Recent versions of Office do not support anything except text, RTF and Word 97 and newer. The older formats (especially the infamous Word 6.0/95) were deemed a security hazard a while back, so MS cut support for it. On Windows those filters aren't installed by default any more, but you can still install them - not so in Mac Office, that I'm aware of.
Anyway: Easiest way is to use an app that does support Wordperfect, such as
OpenOffice or its Mac-optimized sibling
Neooffice to convert your files to a recent Word format.