My gynac did the first scan around 6 to 8 weeks to confirm the pregnancy and check the heartbeat. Some doctors wait till the dating scan around 7 to 9 weeks. It really depends on your doctor, so go by what yours schedules.
First scan is usually after you get the positive and your period is well missed, around 6 to 8 weeks. They confirm its in the right place and see the heartbeat. Just book your first appointment once you test positive.