Elements External HD Lost Power Cable

Hello all.  I am new here and need you people to help me with a problem if you can.  I have an ‘Elements Powered by WD’ external hard drive which I am missing the power cable for. The model is WD4000C035. The connection on the back of the box is circular in shape. I am not computer literate so the info I can give is very liimited.
Does anyone know where I can get the right cord/cable/whatever it’s called.  I do have the USB wire fortunately.

Thanks everyone for any help.

John Watt, Cape Breton Island, Nova Scotia.

Can you take a detailed digital photo of the connector and post it?

Trying to attaching a picture.  Here goes Sure hope this helps THANK YOU.

Trying to attaching a picture.  Here goes Sure hope this helps THANK YOU

Hey bud, did you see the photo I uploaded?  does it help?