Yes, you can use the Import>From Files and Folders command to bring all of the photos on your external drive into the Elements 2024 catalog.
- In the dialog that opens, select the external drive or the main folder that contains your photos
- Make sure that you check the box to include sub-folders
- Click the Get Media button

Depending on the number of photos you have, the process can take a while. Once the photos have been imported, it also takes a long time for the thumbnails to be generated. The program will then perform face recognition on your photos so that you can name the people in your photos. The photos will also be analyzed for their content. Smart tags will be applied to each photo that will allow you to search for particular subjects.
However, because you did not make a backup of your catalog, you will probably lose all of the organization previously conducted in Elements 6, such as keyword tags and Albums. I'm not sure about this, and you may be given the opportunity, after the import, to include any saved keyword tags. If you choose this option, the previously saved keyword tags will appear under the Imported Keyword Tags category. The reason I am not sure what will happen is because your keyword tags will be from such an old version of the program. There have been many changes to the program in the meantime and a different database system is now in use.