If the point of this is to do a conversion and then clean up the epub, there is a DOC input plugin to convert from these. See
https://www.mobileread.com/forums/sho...d.php?t=229166 for details.
Alternately, open it in a recent version of Word and save as DOCX. The conversion plugin for DOCX is built-in to calibre, so there is no need to add anything.
There is also a Word addon that allows you to export from Word as an ePub. See
https://www.mobileread.com/forums/sho...d.php?t=213372 for details.
Of these, I have only tried the first, but only to help debug the plugin. There are probably other ways and I suggest asking in either the ePub forum or the Workshop forum for help.