The challenge to answering this question lies in dealing with all the cities named in Numbers that are no longer in existence or that have had name changes beyond recognition.
The Wilderness of Zin is the area known today as the Negev;the southern border starts at the southwest end of the Dead Sea (Salt Sea) across from Edom, which can be seen as roughly the southwestern border between Israel and Jordan. Kadesh-barnea is known today as Ain el Qiderirat and is located just across the border into the Sinai Peninsula. The brook of Egypt is now known as Wadi el Arish. The Great Sea is easy - the Mediterranean Sea.
Moving north along the western boundary of the Mediterranean, Hamah (Hamath) is to the east, inland from the coast in what is now Syria. I am not able to identify the other towns marking the eastern border, but it ends back at the Dead Sea. So the actual territory promised by God to the Hebrew people stretched much further north and south along the Mediterranean coastline.