mac, icloud and photos syncronisation

My current question is: is there a way to get all of my image and movie files I have synced to the icloud from my mac, into the Photos app?

A little background: Over the years I have saved many pictures and videos on several external drives. One of the main drives, which is 1TB is starting to fail. I have gotten it to work on an older macbook. I have been uploading my files from another drive to my icloud, so I can clear this drive, copy the files from the damaged 1TB drive and send them to the icloud as well. It is taking me a long time, because my own macbook only has 250GB storage and everything first needs to upload to free up space, and so on.

Why am I doing this: the problem started because over the years I have put all of my pictures and videos from these disks into the Photos app. But Photos has lost the reference files for many of them. And even when I restore the reference, which seems to be successful, the pictures still show up in the 'smart album' reference file overview and wont sync to the cloud. I have tried many things, among them creating new albums and placing the pictures in there - still nothing. The new album will only show pictures on my phone that are already in the cloud. And the pictures that are just on my computer and on the hard drives, wont upload/sync to the cloud.

It seems to me my only solution is to start 'fresh'. Clear the Photos app entirely and add everything anew.

So I am uploading all my old drive files to the icloud. And from there it would be very nice if icloud could recognise image and video files and put them in the Photos app for me. The only other alternative is to incrementally download the pictures to my laptop again, add them to Photos and then remove them from my laptop again (and download a new batch from the icloud).

Hope somebody has some insights for me!