I think you can ask your optometrist for the pupil distance when you get your prescription. Check to see if they have to give it, in case they try to say they can't.
It might be good to get them adjusted regardless. It'll be a better fit around your ears and nose. My face is wonky, so it looks more symmetrical after I get it adjusted 🙁 Sometimes, an optometrist may charge for it if you bring outside frames, or they might say they don't want to do it in case they break them.