How do I save all of my full sized images to an external device. Images stored in icloud.

Export photos from system photo library to a desired location say download folder in finder and connect an external hard drive to the Mac , then transfer the photos from download folders into the external hard drive , hence all your photo data is saved .

You can select few photos see this article Select and deselect photos in Photos on Mac - Apple Support and delete to recently deleted folder see this article Delete photos or recover deleted ones in Photos on Mac - Apple Support ( its your choice to delete them permanently immediately or after 30 days the photos will be removed from the iCloud server ) .

In this way the complete photo data is still on external hard drive , but the space is reduced in photo library .

See this article to export photos Export photos, videos, and slideshows from Photos on Mac - Apple Support

Second method .

Photos can’t be transferred directly from iCloud to an external hard drive for that you need to set up iCloud photo library see the article https://support.apple.com/en-in/HT204264

And its preferences https://support.apple.com/en-in/guide/photos/pht5156cc968/4.0/mac/10.14 , open finder > Go > home > your user name > pictures either drag and drop Photos Library.photoslibrary to an external hard drive , the second method is right click on Photos Library.photoslibrary and click on show package contents in the upcoming column , you can also drag and drop complete masters folder to an external hard drive that is connected .

Also as per the article https://support.apple.com/en-in/guide/photos/pht6d60d10f/mac

• Manually copy your library to an external storage device: Drag the Photos library (by default in the Pictures folder on your Mac) to your storage device to create a copy.
• See this article also Photos library - Move your Library to an external storage device

Read this : Back up the library in Photos on Mac - Apple Supportsupport.apple.com › en-in › guide › photos › Mac

Hello and welcome to Apple Support Communities tpbtpb77,

We see that you're trying to export photos from your MacBook Pro to an external storage device. We can understand needing to free up space on your Mac, and we'd be happy to help.

Take a look at the articles that we have provided below that can help you accomplish what you're trying to do on your Mac.

How to free up storage space on your Mac

Use external storage devices with Mac

Let us know if you have additional questions regarding this.

Have a wonderful day!