mixing breast milk and formula

Kyra

my son is 7 weeks and is currently only breastfed. has anyone breast fed & gave their baby formula? do u mix it in the same bottle? or alternate breast feeding & formula? i’ll be going out of town & im pumping as much as i can but i know i won’t have enough for him to eat while i’m gone. i’m stressing somebody with advice, please help😬😬