When are you supposed to put a comma in front of ""and""?

Ex I went to the food, hats,and shoes store.

A comma goes in front of “and” during a compound sentence (I saw my friends today, and I went for a walk) or in a list of more than two things (as the person above showed)

He said he had no intention to be involved with any other suspects and that the incident occurred at a news conference 9in in the parking area and was also expected for an hour later and a few days before his arrest and he had a 7child and the two had been killed and two were injured in a c car 33crash incident in a c square on the scene in which the driver of the car parked on a bus at a bus stop in a coma and was also a suspect on a car crash near san jose on the interstate north on a highway from san diego county in new orleans where a woman is being charged in connection with the murder in her home state in a coma