documentclass{article}
usepackage{enumitem,amssymb}
usepackage{multicol}
newlist{todolist}{itemize}{2}
setlist[todolist]{label=$square$}

newenvironment{Ckcol}[1]{begin{multicols}{#1}%
        begin{itemize}%
        begin{todolist}}%
              {end{todolist}%
                end{itemize}%
                           end{multicols}}
begin{document}

   begin{Ckcol}{3}

    item  item 1
    item  item 2
    item  item 3
    item  item 4
    item  item 5
    item  item 6

   end{Ckcol}

end{document}

documentclass{article}
usepackage{enumitem}
usepackage{amssymb}
usepackage{multicol}
usepackage{tasks}
newlist{todolist}{itemize}{2}
setlist[todolist]{label=$square$}%

newenvironment{Ckcol}[1]{begin{multicols}{#1}%
    begin{itemize}%
      item[]begin{todolist}
      }%
      {end{todolist}%
    end{itemize}%
  end{multicols}
}
begin{document}

   begin{Ckcol}{3}
    item  item 1
    item  item 2
    item  item 3
    item  item 4
    item  item 5
    item  item 6
   end{Ckcol}

begin{tasks}(3)
task Foo 1
task Foo 2
task Foo 3
task Foo 4
task Foo 5
task Foo 6
end{tasks}


end{document}