Escape from the Apocalypse, from Exoskeleton Backpack to Gundam

The end is coming, thousands of races invade, and Fang Zhen gets a super backpack system. It can eat parts and evolve infinitely. From a piece of scrap metal to a single-soldier mecha. From a broken car to a land battleship. Everyone thought that Fang Zhen was nothing but scrap metal, until that day, when God came to the world, I activated my backpack and transformed into a Gundam.