- Install the Amazon Photos Amazon Clour Drive application. When it asks you to sync from your cloud to your local, choose any folder in your hard drive.
 - Then, turn off the the application
 - Plug your external hard drive in.
 - In your Finder, go to:
/Users/USER_NAME/Library/Application Support/Amazon Cloud Drive - Open file amzn1.account.#########-settings.json with your text editor, you will see somethings like this: