Hi Krishna,
With the Unity to Unity Connection upgrade/migration License
your ports will carry across just like your user Licensing
If 24 Ports are still enough to support all your requirements
then you should be good to go.
Migrating from Cisco Unity 4.x or Later to Cisco Unity Connection 7.x
http://www.cisco.com/en/US/docs/voice_ip_comm/connection/7x/upgrade/guide/7xcucrug022.html
If you have any licensing related questions, fire off an email to;
connectionmigration@external.cisco.com
Hope this helps!
Rob