How many ultrasounds is safe to receive during pregnancy?

I heard people talking about if you have too many ultrasound is bad for the baby but im not sure if it is true or not.Im currently 16w4 days and had 2 ultrasounds .First when i was 8w2d and the recent is at 16w.Im planning on going for the third one when im around 20-24w to find out the gender.Hope 3 ultrasounds would be fine because i dont want to harm my baby eventhough i love to see him/her so much through u/s :(