Going out of town, how much breast milk do I need?

This is my first child and I’m learning so much as I go...but having to plan to be away from her in September for a week is already killing me. One thing I’m already stressing over is the amount of breast milk I need to stock and leave behind, how do I know what is enough? She’ll be 4 1/2 months when I go out of town. Right now she’s a few days shy of 11 weeks and eats 2-4oz.

Is there a secret calculation or chart that I don’t know about? Lol. Also how do you cope with leaving your LO for more than a work day?