Newtons measure force, while grams measure mass, so there is no answer to your question. (Like "how many pounds are in a meter?") When you talk about how heavy something is, you may talk about either the object's mass or the force it requires be held up against gravity. In that case, on the surface of the earth, F=mg where g is about 9.81m/s^2. So if an object has a mass of 10kg, it has a weight of about 98.1N on the surface of the earth.