I remember when I was young, my teacher taught us if ever in doubt, use the process of elimination; when time allows, exclude all incorrect answers and the one remaining must be correct.
Instead of looking for the actual tomb one by one, it would be better to just blow up this entire sky. That way, without having to search intentionally, the ancient sword inside the only real tomb will reveal itself.
After browsing through the shop interface, I found an upgraded version of the Firecracker Thunderclap. After breaking through to the defensive power of the Earth Immortal Realm, this item had unlocked another layer, including an explosive with power comparable to that of an Earth Immortal Realm.