In a large bowl, combine the uncooked elbow macaroni, shredded cheddar cheese, shredded mozzarella cheese, and cubed cream cheese. Mix well to ensure the cheeses are evenly distributed.
In a separate bowl, whisk together the milk, melted butter, garlic powder, onion powder, mustard powder, salt, black pepper, and paprika until well combined.
Pour the milk mixture over the macaroni and cheese mixture in the Crock-Pot. Stir gently to combine all ingredients.
Cover the Crock-Pot and cook on low for 2 to 3 hours, or until the macaroni is tender and the cheese is melted and creamy. Stir occasionally to prevent sticking.
Once cooked, give the mac and cheese a good stir before serving. Adjust seasoning if necessary.