Both .gmk and .yyp files are projects from a software called GameMaker, which is an app for making simply HTLM5 based games. If any kind of gmk to yyp conversion is possible, it would be done with this software, but unfortunately we have not found any useful information about this.
If you are determined such export should be possible, it might be best to contact their support or perhaps to reach out to to GameMaker online community for help.
Updated: August 17, 2023