Infant formula for toddler

Je

How long can a toddler have infant milk? My daughter is 18 months and has been on soy and breast milk. I’m pregnant now though so I don’t make much breast milk and I don’t want to give her regular cows milk because we don’t drink it and we would be just be running to the store every few days to buy more after it spoils. Should she have toddler milk or can I just buy the first milk and share a container between both kids when the new baby is here?