Are you moving them into an existing CB site or into a new CB site? If new CB site it's mostly a matter of just exporting the data from the database and importing it on the new site. If it's an existing CB site it's basically impossible as you'll have unique id conflicts in basically every table. It's doable, but we're talking significant amount of work to do that. For CB database tables they all begin with the following.
_comprofiler
_cbsubs
_groupjive
If you're moving Joomla users as well it gets even more complicated as you need to deal with usergroup assignments, etc.. Joomla users would need the following tables.
_users
_user_keys
_user_notes
_user_profiles
_user_usergroup_map
If using custom usergroups then you need to handle those missing usergroups as well on the new site.