Does anyone know how to calculate conservation of momentum?

i have 6 physics problem that involve calculating momentum. like this problem. a 0.15kg blue billiard bal moving at 8.0 m/s to the right hits a similar red ball at rest. if the blue ball continues at 0.0m/s what is the velocity for the red ball?. i just need to know how to do one. then il be able to do the other 5 .