Steps to migrate:

• In a fresh Drupal installation, enable the migration_exercise custom module.

$ drush en migration_exercise

• Import the configuration present in config/default/sync.

$ drush cim

• A custom content type called Cities is present in these configurations, which will take imported data.
• The json file for importation is present in /sites/default/files/migration_exercise.
• Using drush commands in series, check the migrations and import them in the custom content type.

$ drush ms
$ drush mim --group=cities

Custom Content Entity module usage:

• Enable the cities_migration_entity module.

$ drush en cities_migration_entity

• You will find the new custom Entity by navigating to /admin/structure/cities_migration_entity_types