Sync two picture folders with different names

I currently have 2 computers each with its own picture folder.
Computer 1- Pictures
Computer 2- Photos
Nextcloud Photos

Currently each folder has some same and some duplicate folders / pictures.
In the beginning I had manually copied pictures from Computer 1 to Nextcould photos folder. Since then I have added more pictures to Computer 1. How can I sync all 3 together.
I have the client installed and i selected Pictures folder and Nextcloud photos but only the folders seem to sync not the content.

I think the best possibility is to copy all picutres in one new folder.
If you already have the photoes in your nextcloud you can use the app “Duplicate Finder”
But i think there is also free software for finding duplicates for you desktop operating system.

Please sort your pictures in folders and subfolders like “time” or “action”