Delete and perform a fresh install of WordPress

The wordpress importer / exporter should work for this task (maintaining post dates and comments), but it’s better to test it before deleting the online blog.

My advice is to create first a fresh install in a folder (so you’ll can temporary reach your new installation at www.yoursite/folder/ ) and test if everything works fine importing post to the new location. Just then you can delete the old blog and move your index.php to the root (for detailed explanation on how handle wordpress installation in a folder refer to https://codex.wordpress.org/Giving_WordPress_Its_Own_Directory ).

This way you can test first the migration and then substitute the old blog with the new one when everything is done.