Upgrade the CB 1.x install to CB 2.x then you can move database data manually using phpmyadmin or whatever database software of your choosing. We've no official method for doing this so it's entirely manual. Upgrading to CB 2.x ensures all the database changes between CB 1.x and CB 2.x have been applied. It's recommended to do this on a clone of the site so you'll know what to expect when doing the actual upgrade.