Western Digital My Passport 1TB some issue

I was backup-ing 1 folder around 300,000 files (text and website files) around 3 gb , to 2 seperate hardisk at the same time, it shows 2 hours for each, so i leave it run and do other thing, suddenly 1 hardisk disconnected, I have trouble connecting back, upon keep trying, it connected but i realise something, files cannot be deleted.

So did a restart for my computer , right now the lock sign appear ,after logging in or 5 sec , the whole things disappear not detectable. I wanted to use smartware to scan the hardisk but couldnt detect.

Any idea what happened? Is there any way I can use this hardisk again, or format it?

Be sure to connect the Passport USB cable directly to the PC, avoid using extension USB cables or USB hubs, since these can cause power inconsistencies. If the problem continues, try using another USB cable.