I'm 21, I'm about 5'7 and weigh 140 lbs, and I look younger than I am

I've never been to a club but I'm looking at pictures from clubs in my area, and these guys and girls look soo much older than me.. I dont know if the girls would even take me seriously... I mean most of them look older and they'd be taller than me in heels too I'm guessing...

What do I do?