I HAVE 50gb icloud but my wife has 2TB - how can I get rid of my 5gb plan and be part of 2TB plan (not sure if 2TB are family or personal)

not sure if 2TB are family or personal at this moment.

Ask your wife.

See the following Apple articles:

Set up Family Sharing -> Set up Family Sharing - Apple Support

What is Family Sharing? -> What is Family Sharing? - Apple Support

Make sure that each family member has a unique Apple ID

Make sure that each family member has a unique Apple ID - Apple Support

Share iCloud+ with your family > Share iCloud+ with your family - Apple Support

1) I just cancel my 50GB ? and re-upload data from the phone to family plan?

what happens if some of my data is only on my 50GB cloud? How to bring that to 2TB family cloud?

See -> Share iCloud+ with your family > Share iCloud+ with your family - Apple Support

👉 Switch from your personal iCloud+ plan to your family plan

When you share iCloud+, any family members using the free 5GB plan are added to your family plan automatically.

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.

2) are all members seeing other's cloud data or not?

See -> What is Family Sharing? -> What is Family Sharing? - Apple Support

👉 Everyone's personal files and preferences stay private

When you share iCloud+, family members can't see each others’ photos, files, or documents. And when you share other subscriptions like Apple Music, Apple Fitness+, or Apple TV+, each person sees their own preferences and recommendations — not the whole family’s.

Want to keep purchases private? You can hide individual items.