Switching from Apple One Premier to Apple One Family, but need additional iCloud storage

I currently have an active subscription for Apple One Premier which includes 2TB of iCloud Storage. I also have a new subscription from Verizon for Apple One Family which only includes 200GB of iCloud Storage. I would like to cancel my Apple one Premier subscription and only use the Apple One Family subscription, but need to also add the 2TB iCloud storage option I currently have with Apple One Premier. I do not see an option to add the 2TB iCloud storage in Apple One Family, probably since I already have it with Apple One Premier.

How should I go about shutting down my Apple One Premier subscription and adding the 2TB iCloud storage option with my Apple One Family subscription? I do not want to loose the existing files for me and my family that I have in iCloud today, which is around 600GB.