HTML documents can simply by imported to Microsoft Word or other word processor with support of DOCX format and saved as a .docx document. The original HTML formatting will be converted to XML based one in DOCX. It might not be perfect, especially for HTML files not generated by Word, but more or less works. Once html to docx conversion is done, it might require some manual editing though to cleanup the file
Open HTML file Open DOCX fileNote organiser software
One of the many available document converters