how do i move photos on a external drive into iCloud photos

Open your library in Photos.

Set the library as the system library (Photos > preferences > general) -- you can only designate one system library

Enable iCloud Photos (Photos > preferences > iCloud)

First back up your libraries as they now are.

Start with the smallest library. Set that as the system library, and set icloud preferences (as shown above).

WAIT - until that library has synced. Depending on the size of your library that can take days or even weeks. My 50GB 5000 item library took 48 hours. Leave your mac on 24/7, connected to power, with sleep disabled and the photos app open. The sync status at the bottom of the all photos view will give you an idea of what is going on - but it is normal for that not to change for long periods of time.

When that library has synced repeat with the next largest library and so on.

Note - each library will get bigger as it gets merged. (Photos will be both in iCloud AND in the currently syncing library). Depending on the size of your libraries you are syncing, you may need to move already synced libraries to an external drive so as not to fill your hard drive. See

https://support.apple.com/en-gb/HT201517

Obviously you will need enough iCloud space for all your libraries.

Do you only have iPhone photos in your system library?

Photos on your mac in any other library won't upload.

If you have photos in your system library that are not from your phone, and they are not appearing in iCloud first check photos preferences again.

Is the circled button greyed out? If not, click it. Also make sure you have "copy items to library" selected:

Then check the iCloud tab, does it look like this?

You can't sync multiple libraries with iCloud.

You can only sync one library as the system library, and that is the only one that will sync.

If you make each one the system library in turn, they will all sync with iCloud, but then you will merge all your libraries into one big library on your mac also. (There is only one library in iCloud)