Several mountains together form a mountain. A few of these combined form a mountain system. Several systems combined form a mountain, which can stretch thousands of miles in length.

Mountain belt

Explanation:

got it right on edge

When the several systems of mountains combined they are called as the belt of the mountains or range of mountains. They do have the similar characteristics in terms of their structures, formation and the way they are aligned. Himalayas are considered as the highest mountain range. Another example is Appalachian mountains.