I have a WD external My Book hard drive which has my back up on it.
I powered it on, plugged it in to my laptop and it showed up in device manager but not in windows explorer. The laptop is running windows 7 64bit.
I then tried it on my desktop computer which is running XP but it was exactly the same .
The option to Safely Remove Hardware is available on both the laptop and Desktop.
How can I get access to the files on it ?Simple answer is:  the cable is broke.
You can LOOK in the WD User Manuel. Look for tips to  howto know what is song,
https://www.wd.com/content/dam/wdc/website/downloadable_assets/eng/user_manual/4779-705107.pdf
Try to download it if you need it.
Look in chapter 8.
Hi

I would first check in disk MANAGEMENT that the drive is SHOWING and is healthy from here you may just need to ASSIGN it a drive letter. Search on Windows for      Disk management

Are you sure that you didn't use the wd toolkit to password protect the drive? If you did then you need the wd tools loaded to access the drive.

If all else fails you could download this program  https://www.reclaime.com/
It will scan the drive for files for free, but it costs to recover.