There are TWO passwords involved in the setup process:
http://kb.netgear.com/app/answers/detail/a_id/20912/~/installing-a-netgear-wn3000rp-wifi-range-extender
At Step 4 you're entering the password to access the extender's settings (which is, indeed, 'password').
At Step 6 you're entering the passphrase (a.k.a. password or security key) for your existing network. If it's not been changed it should be on a label on the side of your existing router (NOT on the extender). However if your internet service provider sent your router to you they might have changed it to something different. (In which case it will be in the letter that came with the router, or on its box. Your ISP should also have retained a copy of it, so that they can tell you what it is).
At Step 7 make sure that you check the 'Use the same security mode' box.