I think it's one of these situations when you won't know until you try as every LO is so different.
If he doesn't have any milk protien issues then ordinary formula should be fine, but if you have bought the easy digest that should be fine too. He may refuse it as it tastes so different to BM so you may need to express and mix it, then gradually reduce the amount of BM/ increase the amount of formula to get him used to the taste.
IMO I would just go for it, offer him a bottle and see what happens.
HTH!
Laura