I am trying to lose weight but I don't no how much carbs I should eat a day??

Cutting carbs will not magically make you lose weight, but if you replace refined and sugary carbs with protein and fat combinations, you'll find you feel fuller and less inclined to overeat. But it all comes back to calories.

I suggest you cut out the white carbs from your diet (sugar, flour, bread, pasta, rice, potatoes, boxed cereals) and replace them with green veg. Just doing that will cut a significant amount of calories and increase the nutrition and vitamins in your diet without altering the size of your meals.

Base your meals on oily fish, eggs, fresh meat and chicken, lots and lots of green vegetables, dairy, olive oil, nuts, fresh whole fruit (not juice) and very small amounts of whole grains like oats, you should lose weight without suffering. Eat when you are hungry, stop eating as soon as you are no longer hungry. Wait till you are hungry before you eat again.