Hello there Tipra,
I am sorry that you are having issues with your WD external drive. Have you done some troubleshooting up until now?
What is the exact model of your device? Keep in mind that by opening the enclosure you will void the warranty. Furthermore, the drive may have hardware encryption and you will not be able to access the data.
I would suggest you to start with testing the device with WD Data Lifeguard Diagnostic tool and see if it will pass the tests.
Also, there is a possibility that this is a USB controller drivers issue. I would suggest you is to uninstall them, reboot and install them again. Another thing you can do is just to try the drive on another PC.
Here is a guide from the WD community with some more...