You're absolutely right. You aren't supposted to end English sentences in prepositions but, English speakers do it anyway. Putting the preposition in front like in, "From where are you?" sometimes seems strange to English speakers. I personally make an effort to speak English properly, but it is more common to hear sentences to end in prepositions. Mostly, you'll see people ending their sentences in more formal English such as in school reports, business and law documents, important meetings, and anywhere else where it would be necessary to be more proper and formal.

You can say also from where you are or with whom you arrived and it will not be mistake. There is two way of constructing such sentences. First, when preposition goes before question word and another, when preposition is in the end of the sentence.