Help with a silly problem.

Hi all, Tomorrow my girlfriend and I (24m) will be getting dinner and then going to a bar by her place for drinks. Here’s the issue… I’m autistic and have pretty bad social anxiety, especially in situations I’ve never been in before. I don’t have many friends and have only been in a bar once or twice in my life. I have absolutely no idea how to order at a bar or even how anything works. I drink and I know what I like but I still have absolutely no idea what I’m doing and it’s freaking me out. I feel really silly but i guess it wouldn’t hurt to ask on here for some help.