Pap smear

So I’m going to a teen clinic in a couple weeks for an IUD. I want to ask the doctor this but afraid I may forget. I am sexually active. My mom believes I should go to a regular gynecologist and start getting Pap smears. Do gynecologists recommend getting them once your active or when you turn 21 (I think that’s the age?)? I’m going to make notes so I remember to ask but what have you guys experience, did you get them done once you were sexually active (if you’re in your teens)? I’m 17 btw