I have been paying for 200 gb of icloud, my wife just purchased 2T and I want to do family share on her icloud and cancel my 200 gb, how do I do it

See the following Apple Support article for information on sharing an iCloud storage plan: Share iCloud+ with your family - Apple Support

Note that you don't cancel your plan. See the following from that same support article:

If a family member is already paying for their own iCloud+ plan, they can choose to switch to your plan or keep their own and still remain part of the family. When they switch to the shared family plan, they get a refund for the remainder of their personal plan. They can't keep their current plan and use the shared family plan at the same time.