How to migrate Closed User Groups from AEM 6.2 to AEM 6.3 using Migration Tool

Statement - Closed User Groups Migration Tool for migration existing CUG content.Assuming if you have upgraded the AEM older version to AEM 6.3 version.
Environment - AEM 6.3 GA

Solution:
Go to the Felix console URL: http://localhost:4502/system/console/cug-migration

Enter the root path you want to check CUGs for, and press the Perform dry run button.
This will scan for CUGs elligible for conversion in the selected location.
After you have reviewed the results, press the Perform migration button to migrate to the new implementation.

Note:
For AEM installations upgraded to AEM 6.3 it is important to ensure that only one CUG implementation is enabled. 

The combination of the new and the old, deprecated CUG support is not tested and is likely to cause undesired behavior:

collisions in the Sling Authenticator with regards to authentication requirements
denied read access when the ACL setup associated with old CUG collides with a new CUG policy.

If the migration is performed on a publish instance, please enable the Adobe Granite Closed User Group before performing a migration. 

Reference: https://helpx.adobe.com/content/dam/help/en/experience-manager/6-3/sites/administering/using/security-custom-user-groups/_jcr_content/main-pars/download-section/download-1/cug-mapping.pdf