What is a pass code,for this next up date.never been asked that before

The passcode you need to enter is the passcode you set on your device. It is the passcode that you enter when you turn on your iPad or awaken it from sleep after and Auto lock.

If you do not know or remember your password and did not store it somewhere then you will have to restore your device.

http://support.apple.com/kb/HT1212

Chances are you are entering a wrong number. I've updated several devices and had no problems entering the passcode. If you can't remember the correct passcode you will have to restore your device as described in the link I posted.