Breastmilk storing

Im puzzled. Can unused breast milk that is in the chiller still put in freezer? What’s the best method to heat up the milk in freezer? Can i just take it out from freezer and use the milk warmer device? If my milk supply is low, what’s the best method to store milk in freezer? Is 40ml milk very little for each individual pump for each side of the breast? #firstbaby #theasianparentph