Look at the circuit attached to your previous post.
You had confused me, in your post you talked about a 12V siren but in the schematic the supply is clearly labeled as 9V.
If it's 9V then 179 would be fine but if it's 12V it'll be too low.
I wouldn't recommend running the LED at 30mA which is its maximum current rating, ideally it should be less than that.
I'd recommend running at 20mA, in which case you want a 250R resistor, although you'll find 270R easier to get hold of because it's the next standard value up.
All you need to do is use the same schematic, I posted above but replace the 680R resistor in series with the LED with 270R.