How do I change a phone number? It used my iPhone number instead of my iPad #

Your ipad does not have its own number. It will use whatever iphone number is asscociated with the apple id you're signed in with.

You can change the send/recieve info at settings/facetime

Well the ipad is not phone, so it can't use a phone number. When using messages however, it will/can use the your iphone number thats asscociated with the apple id that you're signed in with.

about messages

http://support.apple.com/kb/HT3529