Where did the second beast require people to receive its mark?

Answer: On the right hand or forehead

All were required to receive a mark on the right hand or forehead, so that no one could buy or sell without it.

“And the second beast required all people, small and great, rich and poor, free and slave, to receive a mark on their right hand or on their forehead, so that no one could buy or sell unless he had the mark—the name of the beast or the number of its name.”— Revelation 13:16-17 (BSB)