How to translate clothing sizes from male to female and female presenting

Hey, so I might be socially transitioning soon (only during the weekends) and going to get some clothing…I don’t know how I should translate all the Mae clothing sizes to female especially the under wear stuff. T shirts I usually wear extra large but I like loose oversized things already so I don’t know if I just choose the largest things or no….

Also side thing I’m a bit terrified of the fear of any of my students or other co workers might clock me in public if they see me, is it still a good idea or should it air to come out at my school district first?