Open system preferences > iCloud and uncheck the box of iCloud Drive a pop up window appears , showing to keep a copy of documents , and remove from the Mac .
( a ) if you had clicked on keep a copy , they will be archived in home folder that can be viewed by clicking on finder in the dock , take cursor on top menu bar > Go > Home > your user name > iCloud Drive ( Archive ) .
( b ) if you had clicked on remove from Mac , the iCloud Drive box will be unchecked , you have to again click on empty iCloud Drive box it will turn on , make sure you had always turned on desktops and documents box Use iCloud Drive to store documents on your Mac and iOS devices - Apple Support