xmlx to xlsx conversion is probably searched by users that found some very old / rare file type from Excel (Mac version perhaps) or file that had its file suffix manually changed with a typo. You can always try to read .xmlx file in Excel and see if it works, if not even the direct data loading does not work, then these files are not from Excel and you do not have to look for any kind of converter, it won't work.
Updated: July 19, 2023