Ajay,
If you are using Migration Manager, it will backup DBs, Mails, data & config. If you face problem migrating DB follow these steps:
On the old server side, a connection should be established to db server with the parameters defined in the configuration of the source Plesk server. Make sure admin account defined in the connection config has rights for all user's db. On new server, db server must be configured first in Plesk. Only then db connection could be established for migration.