In my high school English class, I learned that "where", "when", "how" can be used to replace "something+preposition+which" depending on the context. But I sometimes see sentences like
New York is where I came from.
I asked my teacher, and she said it's equivalent to
New York is the place from which I came from.
I don't believe this is correct! But I'm not sure. Is this correct? Can "where" be used as "from which" in this context? If not, what is the appropriate replacement for the "where" in the first sentence?