It would probably depend on what the other person means by "will not help". Regarding unsafe illegal abortions, ERI did a helpful podcast on that. Search for "Responding to “Back-Alley” Abortion Arguments" on this site (I can't seem to post links without my post getting auto-deleted). If they mean that restricting abortion won't impact the number of abortions, there is abundant evidence that is not really the case. See: bit(.)ly(/)3rF9qC8
bit(.)ly(/)3735yDq (remove brackets) The reason pro-life people try to make abortion illegal is not simply because it might mean fewer would women have them. It's because abortion is an unjustified act of violence against an innocent human and as such, permitting it is a human rights violation. Just as it would be wrong to legalize spousal abuse (even though it still happens) because it would be a profound violation of women's rights, it would be wrong to legalize abortion (even though it still happens) because it violates the unborn child's rights.

It would probably be best to first ask them what exactly they mean by "will not help". Do they mean it won't help women with their circumstances, or that it won't stop all abortions, or that just as many women will have abortions if it's made illegal? For the latter point, there's a lot of good research that shows banning abortion (along with other restrictions) does indeed result in fewer abortions. https://blog.secularprolife.org/2017/08/pro-life-laws-stop-abortions-heres.html
https://blog.secularprolife.org/2018/07/more-evidence-that-abortion.html But I hope ERI does a podcast about it someday, as it would be a great topic.