When you say mozzarella, what do you mean? Did he bring home balls of the fresh stuff sitting in whey brine? Did he get bricks of the dried stuff? Bags of the shredded dried stuff? Lots of things get called mozzarella commercially... knowing what you've got would help us come up with recommendations...
see e.g.: https://www.foodrepublic.com/2015/10/01/12-types-mozzarella-know-love-melt/ and https://www.thekitchn.com/whats-the-deal-with-low-moisture-mozzarella-and-when-to-use-it-256664