[Dovecot] how to backup inboxes in dovecot ?

I upgraded my server from Mandrake 9.2 (Imapd , postfix & SQ mail) to Fedora core 2 (dovecot, postfix & SQ mail) i backed up /etc/passwd , /etc/shadow files & all home directories of users account on my server .. after resotration & configuration of the servers everything seems to work , except users email they had on the server saved :( man this is embaracing .. can u tell me wat i did wrong ? where were the mails stored .. & wat is the right way to do it ?

thanks