You cannot sync the two directly. You have to get the content thats on your phone, onto your computer. Once there you import intoi itunes, then sync to ipad. This is not all easy, depending on the type of content, how it was obtained or purchased. Simply backing up, does not transfer any content from one device to the other, you have to sync the content.
iTunes syncing
How to transfer or sync content to your computer
http://support.apple.com/kb/HT1296
How to sync iphone to computer
http://ipod.about.com/od/iphonehowtos/ss/syncing_iphone_4.htm
Syncing multiple devices with one computer
http://support.apple.com/kb/HT1495
IOS: Syncing with iTunes
http://support.apple.com/kb/HT1386
Apple - Support - iPad - Syncing
http://www.apple.com/support/ipad/syncing/
ITunes: Syncing media content to your iOS devices
http://support.apple.com/kb/ht1351