The impact time for a particular collision is 3.0 × 10-3 seconds and the impulse in the collision is 0.30 newton seconds. what is the force of the collision?

There are several information's already given in the question. The answer can be easily deduced using those information's. 

Time = 3.0 * 10-3 seconds
Impulse = 0.30 newton
Then
Force = Impulse/Time
          = 0.30/3.0 * 10-3
          = 1 * 10^3 newtons.
I hope the above procedure is clear for you to understand and it has actually come to your great help.