How many lamps were set on the golden lampstand?

Answer: Seven

Six branches extended from the lampstand's sides, three on each side, and it held seven lamps.

“Six branches are to extend from the sides of the lampstand—three on one side and three on the other. Make seven lamps and set them up on the lampstand so that they illuminate the area in front of it.”— Exodus 25:32, 25:37 (BSB)