I am in Chutz Laaretz in camp - I’d like to know when taking a walk on Shabbat is Assur based on Tchum, and how far is it in feet?

Within a built town or city – one can walk as far as he wants even without an Eruv as long as he doesn't carry anything. Outside of the borders of the town – or in your case outside the premises of camp (assuming it in the middle of a forest / woods etc.) you have extended 2000 Amot to any side around the camp, which are about 1100 Yards, to walk within.