My friend has a 2002 Malibu and wants to know how many quarts of transmission it needs

Put in the same amount that came out. If you drop the pan and change the filter, it will take about five quarts even though the entire system holds more than twice that amount, including the torque converter. Buy your fluid starting with a gallon, it's cheaper than by the quart. Top it up slowly so it is not overfilled. Check level while idling in Park or whatever it says on the dipstick. Use the correct fluid.