The only way *.wbk files could be converted to *.html documents would be to first recover these using Microsoft Word and then using File ► Save as.. function to save to HTML format. It is unlikely another program would be capable of this, as auto-backup documents (*.wbk) can only be recovered using Microsoft Word.
Convert Microsoft Word document save backup to HyperText Markup Language web page.
We have found 2 software records in our database eligible for .wbk to .html file format conversion.
Microsoft Windows software - convert wbk to html on Windows
One of the most popular word processor program from Microsoft Office suite
Convert from wbk file format
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 wbk to html. 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.
Apple macOS / Mac OS X software - convert wbk to html on OS X
A Mac version of the popular word processing application