The obvious choice for this conversion would be to use the original software for .mwd documents - Mariner Write. However, it is only available for OS X, so if you do not have access to a Mac computer, you ma have trouble working with this document. It seems the LibreOffice Write supposedly supports at least some version of .mwd documents, so it's worth a shot.
Found 2 different conversion types using the same filename extensions.
Conversion mwd to doc type 1:
Convert from Mariner Write document file to Microsoft Word 97 to 2003 document.
Multiplatform software - convert mwd to doc on any platform
Full-featured word processing and desktop publishing tool from LibreOffice suite
File type (from-> to)
Convert from mwd file format
Mariner Write document file
Microsoft Word 97 to 2003 document
The tables with software actions are a good pointer for what a certain program does with various file types and often may give users a good hint how to perform certain file conversion, for example the above-mentioned mwd to doc. However, it is not perfect and sometimes can show results which are not really usable because of how certain programs work with files and the possible conversion is thus actually not possible at all.
Conversion mwd to doc type 2:
Convert from Mariner Write document file to Document file.
Apple macOS / Mac OS X software - convert mwd to doc on OS X
A word processing program for Mac