Dead battery

car set for 3 weeks had to replace battery now car will not start can’t hear fuel pump when try to start 2002 pontiac grand am

Batteries go dead for various reasons. Dead cell, caused by lead in the plates flaking off and shorting the other plates when the flakes accumulate in the bottom of the cell. Low fluid level does not allow the battery to charge properly. Someone put regular water instead of distilled in the battery. The alternator or voltage regulator are not giving a full charge to the battery. Or, there is a vampire on the battery, such as a cell phone or a tom tom that drains the charge while the car sits. On some of these newer cars, the electronics are too complicated for an ignoramus like me to understand, so I dont know why your car wont start now. did you clean the terminal lugs when you put in the new battery?
And for the sake of the more knowlegable fellas, how many miles on this car, and have you followed the service schedual?

Did you have the new battery charged before installing?
Did you clean all the cable ends when installing the battery?
When you try to star it, does the starter motor turn the engine?
Can you hear te fuel pump with the key in the ON position?