What are the obvious things to import?
Mail, Feeds, Contacts, Settings, Bookmarks, Passwords. Maybe there are a few more.
Why in the world wouldn't even a brain dead software designer strive to put ALL these things in one place? Not scattered around for us to hunt down. So we can back them up, transfer them elsewhere, etc.
This is a perfect example of something in the computing world: NEVER trust someone skilled in tech to have the slightest idea of the most simplistic organization and communicative skills. Everything they do must be checked and checked. They may have skills in their tech area. But often not in other areas. Yet management doesn't get this. The biggest companies have some of the dumbest most illogical designs in their sites possible.
Are you trying to import into Opera? From where? Most of Opera's critical data for the user is in the profile, which can be located on you computer by clicking on the Opera menu in Opera 23 (the latest stable version of Opera), and then on "About Opera."