There have been several changes to the database (table names, additions, etc.) since that version. you will need to get your version upgraded to at least 6.1.6 in order to start 'migrating' to D7.0.6. If you have some time, I would suggest creating a copy of your 'live' site and perform this upgrade in a 'sub-directory' or locally. You are up for a challenge either way, especially if you have some custom modules.