What power adaptor should i buy?

WD External Drives External Drives for PC
1

I have a WD 5000aav external usb hard drive and i need to get another power supply adaptor. what  type should i get?

2

This should help http://wdc.custhelp.com/app/answers/detail/a_id/1378/session/L3RpbWUvMTMyMDE3MTc3OS9zaWQvak9TMVcxSWs%3D

Joe