Worldedit
Worldedit is a plugin we have which can be used to do large-scale edits. On Creative1 any Purchasable rank has access to Worldedit, however, it has a cap at 1000 on the maximum number of blocks edited at once.
If you are not sure how to use this tool, either ask other players, use //help in-game (make sure to type the double slash) or refer to this tutorial by Grian.