How to migrate network manager settings
Network manager configuration file are stored in /etc/NetworkManager.Browse the folder and you can see your defined connections.
Moving appropriate files from this folder to the same folder in new ubuntu will solve your problem.
Use this command to browse the folder:
gksudo nautilus /etc/NetworkManager
As far as I understand /etc/NetworkManager does not contain passwords, so that matter should be dealt with separately. As well as other settings and certificates (e.g. openvpn connection settings) which do not work through NetworkManager.