This season 7 week 1 legendary quest requires you to collect 100 stone at the The Aftermath.

The Aftermath is a new location at the center of the map where The Spire used to be before it was taken by the alien mothership.

There are large rocks all around that area so just one of them will give you the 100 rock required to complete this quest.

The map below shows the location of The Aftermath.

Map credit to fortnite.gg