I'm having problems seeing your attached image Skull. The location of the option is found by starting DCS World, going to your options page and looking for the "Visible Range" option, part way down the other list of options.
Take a note of what you have selected (Low, Medium, High or whatever). Then go find the corresponding Low.Lua, Medium.Lua or High.Lua file in your DCS World terrain folder. Should be here: DCS World \ Config \ terrain.
Change the appropriate file by altering the numbers shown in t.Jacob's first post.
Hope this helps.