Back to work, EBF baby, what do I do?

Amanda
So My baby is EBF and in a month I have to go back to work! 😢 I have to leave her with my mother in law, even though we have very different parenting beliefs, and I just wanted to know how do I know how much milk to tell her to give her during the day. I've been pumping and freezing milk. I'm just afraid she will say it's not enough and take it upon herself to give my daughter formula! Thank you in advance for any advice