deleting catalogues in LR

This is probably too late. But I just read the comment where you indicated that instead of renaming your image files you renamed the folders. Now, that's a different story. In that case all you have to do is highlight the folder in a library module and update the folder location and point Lightroom to the new folder. That would get Lightroom aligned with all the images again, and you can proceed. But, like I said, probably too late.

Based on what I have come to understand, I think your best bet would be to create a new empty catalog and import your images again and just start over. I usually don't rename images. If I'm going to do that, I usually do it when I export copies for what ever purpose they are intended. But I usually leave the master images with their original names. But that's a personal choice, not necessarily the best. By creating a new catalog you will lose all of the editing that you have accomplished to this point. But since you have changed the name of all of your images using your operating system I feel that it would be a nightmare trying to synchronize everything. That's my take on the whole situation. Believe me, the catalog is not your enemy, you cannot fight it, you have to learn to work with it. Until you do that Lightroom can be an absolute nightmare, as you have discovered.

When you indicated that the images are "backed up" on the external drives, I assumed that the external drives were backups and not the original images that you are working on. I assumed that the original images were on your internal hard drive. That is usually what I refer to a backup as being. So please pardon my misunderstanding.

Is Lightroom accessing the original files on the external drive, the ones that you have renamed? Did you rename those files using your operating system?

My impression is that you jumped into using Lightroom assuming that it works like a "typical" image editing program and didn't take into account how the catalog really works. By doing that, you have totally confused yourself. You would do well by stepping back and taking the time to watch a few tutorial videos that are available in a variety of places, YouTube, the Adobe websites, Julianne Kost has excellent tutorials, etc. Get yourself acquainted with what Lightroom Classic is really all about and then just create a new catalog and take a deep breath and relax and start over.

Lightroom works very well if you just learn to work with the catalog and not try to fight it. You have to understand that the catalog is the only file Lightroom opens. It's the only file that Lightroom modifies. When you want to organize your files you have to think in terms of what will work best in the catalog. And when you learn to use the catalog efficiently it will all fall into place and work to your benefit. It seems to me there right now you are fighting the system and it just isn't going to work well.

I must ADD.

You should have only ONE Catlaog as you Main Working Catalog. That is the way LR Classic is designed to work.

It is ok to have other catalogs for testing and such but you should never have more than ONE catalog that ALL of your images are imported to.

You sparate your images by either Folder naming, Date or place. Or if you want all your images in one folder then by Keywords or Collections or both. Or use all 3.

But you should never have multiple catalogs you store different images in that you work with regularly.

I have 2 catalog. One is my Main catalog that ALL of my personal and work images are imported to.

The other second catalog is for testing purposes. Like downloading and viewing images from new cameras that I see in reviews and things like that.

But evey image I have ever shot are in my main working catalog file.

I think you would be happier if you would learn to let Lightroom sort of "take over" And manage everything for you. If you try to just bring images into Lightroom to edit them, changes are simply recorded in the catalog and under normal working conditions don't get stored with the images. And you don't get the opportunity to take advantage of the keywording benefits that make it easy to locate images in the future. Then there's the feature of being able to share images via the cloud if you should ever want to use that option that is connected with Lightroom Classic and Lightroom for the cloud. But the choice is yours. Then again, maybe Lightroom isn't for you. Perhaps you would be happier with Photoshop Elements which is a much simpler system that keeps everything local on your computer and doesn't involve a catalog or database system. I suppose the catalog wasn't such a problem for me because I worked with databases for 25 years at my job at a university, so understanding the concept of the catalog/database came rather quickly for me.

If you are referring to catalogs then you must be using Lightroom Classic because if you are using Lightroom (for the cloud) you don't have access to the catalog really. Images are not stored in the catalog in Lightroom Classic, they are stored in folders on your computer hard drive(s). If you are going to change the name of a file, it should be done within Lightroom. Otherwise, Lightroom will lose track of the image because the Lightroom catalog is simply a database that keeps track of where images are located based on the name of the file as well as where that file is located on your computer. You can choose to create a new catalog and begin importing images again from your computer as well as new images from the cards from your camera. Be aware that doing so will mean that you will probably have to start over with all of your editing unless you go to the library module And choose the option to select all images and write changes to XMP before you decide to create the new catalog. Then after you import the images into the new catalog you could highlight them and in the library module choose the option to read metadata from file. That could preserve some of the work that you have done up to this point.