photos transfer to external hard disk

I moved my photo library to an external hard disk drive. However, When the external hard drive starts and I open the photo library which is in there, all photos seem as if they are in my computer, but when I unplug the external hard drive, nothing is in the photo library. i cant understand why this happened or how i fix this?, the steps that i took from the begining is

1. Attach your external hard drive to your Mac.
2. If you have not yet done so, format the drive. We suggest using the same filesystem format that you are using on your internal hard drive.
3. Open a Finder window and verify that your new storage device is correctly attached. You should see it listed under Locations in the Finder Window.
4. From the left panel in the Finder window, select Pictures.

If Pictures is not an option, go into Finder’s Preferences > Sidebar and check the box Pictures.

5.Right click on the Photos library icon and select Get Info. Verify that you have enough free space for the library on the external drive.

6.Drag and drop the Photos library icon onto the hard drive icon either in Finder or on your Desktop.

7.Wait for the copy to complete. The elapsed time will vary based on the size of your library.

8.When finished copying, hold down the option key ⌥ while launching the Photos app.

9.Click Other Library and navigate to the new location on the external device.

thanks in advance