Hi there Sudipto_1,
I would have to agree with Kiaan_R. Unfortunately, the device has sustained some physical damage. This means that either the enclosure or the HDD itself(or both) is damaged.
If the data stored on the drive is really important, your safest bet would be to contact a data recovery company.
Apart from that, in similar cases, some users take the drive out of the enclosure in order to attach it internally via SATA&power cables.
Keep in mind that this may not work due to various reasons.(connectors, encryption, etc.)
Let me know in case you have some more questions,
D_Know_WD