another physics question (momentum)

alright, so i have a car's mass, its velocity, and the time it took the car to come to a complete stop.

ex: a car 1200 kg going 30 m/s takes 30 seconds to come to a stop (i'm not sure if thats realistic but just bear with me)

OBJECTIVE: calculate the impulse.

i know its just a simple calculation. I know impulse equals the force (newtons) times the change in time. But All I have is the above information, I don't know how many newtons it is.

Would I just do grams x time? I dunno...you know?