How to get a doctor's appointment for accurate reading of how far along in pregnancy?

I recently found out Im pregnant from doing blood test but the blood test does not indicate how many weeks I am along. This is my first time experiencing and I've asked chat gpt, from date of my LMP, I should be 7weeks but I don't know how accurate is that. So, should I get a doctor's appointment to find out? How does a doctor find out? Through ultrasound scan? Thank you very much!