How can I move my family sharing to new iCloud storage plan
Just upgraded to larger iCloud plan but used to have family sharing - how do I move them
to new plan? Do I have to delete old one?
Unless there' something you have omitted to mention that is adding complexity to the issue, when you upgrade your iCloud plan you just changed the old plan. There is no "new" plan.
If you are referring to Apple One, see: What happens to your iCloud storage when you sign up for Apple One - Apple Support