"The girls drink milk."
Translation:Die Mädchen trinken Milch.
Das Mädchen - the girl (singular) Die Mädchen - the girls (plural)
All nominative plural nouns take "die", regardless of gender. Mädchen just happens not to change in its plural form, so das vs die is one of the only ways to tell whether "girl" or "girls" is the intended meaning. (For future reference, all diminutives ending in -chen stay the same in the plural)