since your goal indicates a desire to lose fat, a very high percentage of your carbs should be from veggies, some fruits, and very little from processed carbs like breads, cold cereal, pasta, and refined sugars.
its hard to give an exact figure since I dunno what your diet and daily calorie intake is like right now, but I could toss out 75g as a maximum amount of carbs from NON-Veggie sources a day. every other carb should be leafy and green. watch fruits...the sugar in them adds calories.
also remember that for our purposes, potatoes are not veggies...they are a starchy carb like pasta.