External drive died. Photos are a mess now. Help with organizing them, please?

Wow!

Photos provides each picture with a new unique filename that it can use in its database, where the new filename is associated with the old filename. Unfortunately, you seem to have lost the database. What you are seeing is the original images, not edited or cropped or annotated. All that would have been in the database.

I would import all this stuff into a new Photos Library, and I'd use Smart Albums to do the organization. You can create a Smart Album with the menu item "File>New Smart Album..." Then set dates in the Smart Album like this:

This will get all the pictures from this January. Then, in the sidebar, select this Smart Album and hit ⌘-D to duplicate it, and change the months to 2 and 3, rename, and then do it again 12 times for each year. (Or you could do all the Janauaries, and change the year each time, as you prefer.)

Then you can put them in folders.

The downside of this is that Smart Albums don't work in iPhones, so if you want to synchronize your Photos with iCloud and an iPhone, or if you just prefer non-smart albums, then this: Do a Smart January, select all, then File>Make New Album form selection, and then name it January. Don't duplicate, just change the numbers and do it again, copying and making an new dumb-album with the new month. This will make standard albums with months rather than Smart Albums with months.

What do you think?

Emely, your screenshot of the folder "Full Photo Backup" is just showing the content of the "originals" folder of your Photos Library, not the complete Photos Library.photoslibrary. There should be many more folders and database files inside the library package. Do you still have the complete library?

Where is it now stored? If it is on another external drive, copy the Photos Library.photoslibrary to another external drive, that is compatible with Photos. The external drive should be prepared as described here: Move your Photos library to save space on your Mac - Apple Support

The important points are:

• The file system format needs to be either MacOS Extended (Journaled) or APFS.
• The drive must not have been used for Time Machine backups or have backup software installed.
• The drive needs a wired connection, not accessed over the local network.
• If you can't set the "Ignore Ownership on this volume" flag, the drive is not suitable.

The Photos Library is called a "package," which means it's a folder that tries to keep you from looking inside. They don't want you to mess around inside, because that might corrupt the database. That's not really a problem, here...

To look inside, right-click (control-click) on the Library package, and you get a menu:

This is how I got the contents I showed earlier. You can compare...

It's the other folders, like Database, that make Photos work. Could they be somewhere else in your recovery stuff?

Otherwise, it's lots of Smart Albums....

This is what's inside a Photos package:

Can you find these folders? Some, the little ones at the top, may be superfluous.

I've certainly never tried to reconstruct a Photos Library from disconnected parts...