Just graduated this year and school just came back in 2 weeks ago but how long should I wait to go visit cause of course I'm going to want to visit my friends but my ex who has for some reason been having issues with me or something goes to the same school and I don't want her to think I'm stalking her or something so I know I shouldn't go to soon but how long should I wait to go so she doesn't think I'm trying to stalk her?

I wouldn't wait. There are lots of students in that school, and you probably have lots of friends. Just ignore her if you see her.