I formatted it into a single HFS+J partition for Mac computers, but because I haven’t used it for a long time, I have forgotten the password I set up by which way? This dialog box will appear!Where should I find my password?
Have you used WD Security to setup the password on the drive?
If yes, You can refer the below mentioned link.
The Erase drive process is Data Destructive and cannot be undone. Once the process begins, ALL THE DATA ON THE DRIVE WILL BE LOST!