Hello dear student,
Greetings!
In these kind of questions,  you should remember the concept that force is nothing but the rate of change of moment,  and once you apply this concept,  your life will become easy and you can easily solve this kind of questions.
So ,
Force= rate of change of  monentum =d/dt* mv
=v*dm/dt as v is constant
ThereforeF=Mv =2*3= 6 newton
Thankyou
Good luck