Generally most midwives/obs approve of hand expressing after 37 weeks. Just ensure you're collecting in a sterile cup, then freezing in sterile syringes that are clearly dated.

If you pump, at least save the colostrum and freeze it. Colostrum is all your little baby will need for a few and has the exact nutrients and stuff they need. Their tummies are very very small and don’t need much milk at all so the amount of colostrum your body makes will accommodate to their needs