Alright I'm gunna take this point by point because broadly I understand what you are trying to get at but you have a few details that bother me and I feel derail the whole thing.

But I didn’t make the claim that this was definitely going to happen, just that it was the likely outcome

Me neither, I was talking about historical precedent, not some hard and fast rule of the universe.

based on the common sense assumption that if abortion access wasn’t easy, safe, and anonymous, and involved a significant risk of injury or death for the mother, more women would likely find it less risky to carry their pregnancy to term and give up the baby for adoption

First of all, with the "death or injury" part of this, I don't see why this is preferable. Seems like threatening their lives and happiness in the interest of forcing births. But also, this assumes there aren't other ways this can shake out in the end, and child abuse, abandonment and childhood homelessness, and human trafficking are all part of this topic and all things that increase when abortion is illegal. Your common sense assumption is based on a situationally perfect example, and it doesn't make sense when applied to real world experiences.

if they haven’t changed their mind on it by then.

This is just a piece of that bullshit take that argues women will learn to love their future babies if they are just forced to carry them long enough that abortions are more difficult and less legally accessable. Nah

From my point of view, I find the claim that making abortion illegal would not prevent even a single one from occurring far more incredulous and therefore requiring a higher level of proof.

Good thing I wasn't claiming that then. I'm saying the amount prevented would be negligible, not magically impossibly zero. It would likely be a small amount, and utterly overshadowed by the negative effects of banning abortions.

I honestly wouldn’t know where to start looking for data on that.

Generally any search engine is a good start, although you can go to google scholar if you want more academic and dense results. Then, just look for what experts/doctors are saying. Try to stick to groups that verify each other and are verified by outside groups, individual experts are fallible on who knows what, so trust the experts that other experts seem to trust. Generally unless you want to be a researcher yourself, these are the most trustworthy and direct sources for data and such you can possibly get.