Why is finder asking to authenticate when copying to my external hard drive? macOS Sierra 10.12.6 (MacBook Air) 

I am trying to move a directory/folder from my local disk to an external hard drive. But I get an error that says:


  Modifying "Remote Disk" requires an administrator name and password
  
  To move "&lt;your-folder&gt;", click Authenticate.


But I do not see any button or link labeled Authenticate. Also, I read here there might be a solution involving right-clicking the destination drive then selecting Get Info button. However, there is nothing there I can click.

So how can I move this folder to my external drive?

Full screen capture movie .gif



Click here to see the full screen capture movie .gif.

Step 1.

Here is where I get the error message after attempting to move the folder.



Step 2.

The 'Get Info' window is no help.
@bret7600 correctly pointed out in a comment that this is not an external hard drive. The external drive showed up in the Finder when I originally installed it but it went away after I clicked what I thought was a dropdown menu. I then proceeded under the assumption that the object that remained was what I was really looking for.

I had to reinstall the external drive by plugging it in to my USB. I could work on it successfully after reinstallation.