how do you get the dash cam video from the LAPD after they have pulled you over and it was not lawful
Most LAPD units do not have dash cameras. To be sure, though, you ask for the footage with a discovery request to the prosecutor. But you should get a lawyer to help you with this, and not be doing this on your own.
By subpoena in your criminal trial. Your attorney will do so if he thinks it will be helpful, instead of damaging as it usually is.