Welcome, abd_haidar!
I'd strongly recommend you to see how the external HDD appears on another laptop/computer and also try using a different USB cable. If the drive powers up when you connect it, you should check if it's recognized in Disk Management and Device Manager.
@popatim asked a pretty relevant question about Safety Ejecting it. If you unplugged the hard drive while it was reading/writing data, you might have corrupted the file system.
Keep us posted with the troubleshooting.
SuperSoph_WD