You can click in the viewport where the mountain is, copy the coordinates and localize your cloud to that area. Localizeing is done in a spherical space, so if you need really high clouds, but not so wide, it may cut off top/bottom. Or use a soft simple shape (round) as mask, which will extend into Y eternity (column). Then play with the cloud fractal to get the best shapes within that area. That's one way.