Most doctors recommend doing it around 7-8 weeks so that the baby's heartbeat is clearly visible. Just book an appointment with your regular gynac first, and she will write the prescription for the nearest scan center.
I had mine at 6 weeks because of early complications and my doctor wanted to monitor me closely from day one. Make sure you don't skip this first scan, and also get your blood sugar checked early on just to be safe.
I was so scared that doing it too early at 5 weeks wouldn't show a heartbeat and I would panic! My doctor advised waiting till 8 weeks so we get a clear picture. Please don't worry, just schedule it when your doctor says so you don't overthink like I did.
I had my first one around 7 weeks to check the heartbeat, and honestly it was the only time the baby actually fit on the screen! Now in my 3rd trimester, I can barely see what's what on the monitor, just a lot of kicking legs!
Usually it is done between 6 to 8 weeks for dating and heartbeat. Ask your doctor for a package deal because you'll need many scans later, and doing them at a trusted local lab can save some money compared to big corporate hospitals.
I can only tell you what happened in my case, my doctor scheduled my first dating scan at exactly 7 weeks. It was so emotional to hear that tiny heartbeat for the first time.
