photo transfer

Select few photos https://support.apple.com/en-in/guide/photos/pht40b0be510/3.0/mac/10.13 from system photo library and export https://support.apple.com/en-in/guide/photos/pht6e157c5f/mac to a desired location say download folder in finder and connect an external hard drive to the Mac , then transfer( drag and drop ) the photos from download folders into the thumb drive see this https://support.apple.com/en-in/guide/mac-help/mchl027f1d66/mac

Select the images and use file->export and choose either the originals or an image where you can set the size and compression.

Export from the library to a folder on the Desktop and add that folder to the thumb drive.