On cloud nine (可以写成9）

on cloud nine = very happy
Euphoria= extremely happy
/juːˈfɔːr.i.ə/ extreme happiness, sometimes more than is reasonable in a particular situation:
They were in a state of euphoria for days after they won the prize.

When I got a promotion at work, I was on cloud nine.
When I got married, I was on cloud nine.
Logan was euphoria when he got a new bike for his birthday.
Linda experiences euphoria every time she eats ice cream.