If you have a laser that operates at 3V, DO NOT put 9.0V into it! I am absolutely certain it will fry. Can you post pictures? If you can get another battery/set of batteries that has the same voltage, it should work. I once used a CR2 and AA battery taped together in place of an 18650, and it worked pretty well.
Did you even listen to what I told you? 3 batteries = 9 volts. 9 volts will kill your laser! If you want to increase the power and still have a chance of a working laser, get a 3.6 volt RCR battery. Any more than that is too much.