Question

SI unit of mass is kg. SI unit of weight is newton. If I ask somone about his weight, he says 35kg or 60kg . Why he does not say 35 newton or 60neton.

Answer 1

What they’re answering is their mass.
Their weight will be = g × Mass

The machine on which you normally check weight shows you your mass. You need to multiply your mass with acceleration due to gravity at that place to calculate weight.

But, why are you interested in knowing weight?
Weight of a body changes from place to place. Suppose if your weight is 120 N here on Earth it’ll be 20 N on Moon because acceleration due to gravity at Moon is 1/6 times that of Earth

Your mass is same everywhere in universe.

Answer 2

Weight is to find the heaviness (mass) of an object .
mass is a quantity amount of matter of an object and its SI unit is kg which is the medium amount of matter while Newtons is the SI unit of weight which is then converted in to kg
1kg=10N or 9.8N