...i’m taking it apart and not using the box on it
A 7-LED PRR style signal (vertical, diagonal, horizontal) turns on 3-LEDs at a time. There are different ways the manufacturer could have wired the LEDs so there's no one-size-fits-all answer for the voltage/resistor requirement.
I'd think there's a small circuit board in the box with 4 wires going up to the head. The components on this board will tell you how they drove the LEDs and hence what you need if attempting to bypass their electronics to directly drive the LEDs. Post clear photos of this alleged board if you need assistance identifying/interpreting components. It might also help to share what/how you plan to control the LEDs in lieu of their electronics.