me to use is 184 ohms. (9-3.5)/.03=183.333. However, this is not a common resistor value. A 330 ohm and 470 ohm resistor when placed in parallel equal 193.88 ohms, which is close enough. Resistors come in different watt values. Watts = Volts X Amps, 9 x .03 = .27W. Use 1/2