Welcome to the forums!
Can you clarify a couple of points for us?
1. There is no Ubuntu release called "12.01" so do you mean 12.04 or 12.10?
2. What method did you use to upgrade? (If your answer to #1 was "12.10" know that an upgrade directly from 10.04 to 12.10 is unsupported.)
Hopefully you made a backup your data before starting the irreversible upgrade process
but if not your Evolution files are all stored in ~/.local/share/evolution I believe; probably a good idea to make a backup of that folder now, then you can proceed with the process of trying to import them into the new Evolution (since you are now using 2 years newer Evolution a few things might have changed).