We would highly recommend using undiluted baby bottle detergent together with a baby bottle brush, thoroughly wash and clean the bottles and teats (includes the crevices) to remove all forms of milk.
Do note also that as breast milk has been stored in the fridge, the composition of the breast milk may get segregated after some time. As such, do swirl the content to ensure that the breast milk is well mixed after warming up as this will help to prevent fats in the breast milk from clinging onto the bottle and harder to be washed off effectively.
Check out our video tutorial here for a step-by-step visual guide: