You can export the .qb2006 file to a .qbb file to QBB using the File ► Backup to QuickBooks Windows function in QuickBooks for Mac, which is what qb2006 to qbb conversion most likely refers to.
Always be careful when restoring older backups, as they might overwrite your existing data. Also, it is not possible to use new version of the format in the previous version, i.e. you cannot open .qbb file exported from .qb2012 in Quickbooks 2011 etc.