How much walking do I do to lose weight?

I’m fifteen. I don’t want the lecture on balanced diets I am only eating salads and fruits and drinking water I don’t care if I need other things. I’m also having vitamins and milk. But how much walking on the treadmill do I have to do a day to lose weight (in time and/or calories) Ty
No I don’t have a eating disorde. I admit it I’m fat and trying to lose weight.