I have my 34 week checkup today and I know I'm getting a c section for sure from previous ones. I…

I have my 34 week checkup today and I know I'm getting a c section for sure from previous ones. I don't remember which appointment they had me choose a date for it. I know they do it at 39 weeks but i don't know when i get to choose the date if that makes sense? Can anyone refresh my memory on that? Lol