You don’t need “in”. I am confused, aren’t Hangzhou and Ningbo different cities in Zhejiang?

“My hometown is”, “My home is in”, “I live in”.

It is still correct. For instance I am from a city named Provo, in the state of Utah. It’s fine to say, “my hometown is in Provo, Utah.”

Actually, both are correct. Native English speakers would use either of those ways to say that.

My hometown is Hangzhou.