If I pump out my bm on the 1st and kept it in the mini fridge, can I still feed my LO? It's already 4 days

Refrigerated milk can usually be kept for 3-7days. However, not too sure what is the temperature of your mini fridge. As a reference, the guideline is for fridge that is 0-4degrees. I have friends who had went on short work trips and kept their expressed milk in hotel mini fridge which they have brought back. I think you can try warming it up and doing the taste test before feeding to your baby.