Just started 3 multisite networks - need to move over users too!

I just created three multisite networks for all my sites (about 30).

- one for client sites
- one for one single client with 4 of their own sites
- one for friends and family

On the client site network, I brought over all my sites, but no users were brought over. I need to bring over all the users from those client sites. How do I do that?! Please help!