Use the adverb whence as an old-fashioned way to say "from which" or "from where." If you found a hundred dollar bill on the ground, you might ask, "Whence did this money come?"
Not many people use the word whence these days — you're most likely to hear it in a Shakespeare play or if a speaker is trying to sound especially formal. Many people say, "from whence," as in "Throw that fish back in the sea from whence it came," although strictly speaking the "from" is unnecessary. Instead, a dinner party guest could ask, "Whence came this delicious fish?"