Nipple size for bottles?

So we were handed down 12 dr brown bottles. I’m not sure what size the nipples are on the ones we were given but I want to buy all new ones for our baby either way. Should I buy the preemie or the size 1 nipples ??

I plan to nurse initially but I will have to pump since I’m going back to work after 12 weeks so he will be given bottles of expressed milk as well.