Enable MP3Tag to show JPG-files. Go to Tools => Options => Tags => Restrict incoming files to
and add *.jpg to the list.
Read all folders into MP3Tag.
Set the filter to "%_extension% HAS jpg
Now you see only the JPG-files.
Define an action:
Type: Format Value
Field: _DIRECTORY
Format String: %_parent_directory% - Covers
Always test this and other suggested solutions not with your original files and structure but within a test-environment.