How many types of children pediatricians is their?

A paediatrician is the name for a "children's doctor" who does exactly the same job as a General Practitioner, but only treats children. In this context, there is only one type of "paediatrician".

However, you can get "paediatric" doctors specialising in all areas of medicine - e.g paediatric cardiologist, paediatric hepatologist etc...

In short, a "paediatrician" is a general children's doctor, whereas a "pediatric (something... ) doctor" is a specialist children's doctor. There are many different types of "paediactic" doctors.