Question

Is this a prepositional phrase: The citizens and the newcomers met downtown in Whoville.

If yes, where. If not, how can I turn it to a prepositional phrase?

Answer 1

"In Whoville" is a preositional phrase. It indicates where or when. A prepositional phrase will begin with a preposition and end with a noun.
In= preposition
Whoville= noun

Answer 2

well yes since a prepositional phrase shows location
where: Downtown in Whoville.