[Koha] How to upgrade koha

Hi to all I need to know steps to upgrade koha, I have backup to koha 1.2.3 and need to upgrade to koha 3 but i did not know how to convert data to koha 3, i read about convert by marcedit and read convert by upgrade to koha2.2.0 and to koha 2.2.8 to koha 3 please i need the steps to do upgrade please if any body know send to me all steps to upgrade. thnks John Smith _________________________________________________________________ Show them the way! Add maps and directions to your party invites. http://www.microsoft.com/windows/windowslive/products/events.aspx