How to see app users who have cancelled their subscription on iOS?

AFAIK, you have to send a notification at the time of unsubscribe.

Get some hints here: https://qonversion.io/blog/push-notifications-for-subscription-apps-to-win-lost-customers-back/

thank you for this, however I'm referring to how to see a list/graph of users who have cancelled their paid subscription plans. Is there a section in App Store Connect for this or somewhere else we should be looking to see the number of users and when they cancelled?

With help of App Store Server Notifications you can receive notification DID_CHANGE_RENEWAL_STATUS https://developer.apple.com/documentation/appstoreservernotifications/app_store_server_notifications_v2