laravel method not allowed exception with form attribute target="_blank"

My codes result on view woks well and has no error but after i am generating reports of my records from a form submitted from one page and result of the submitted form to another page. it display data well and no error but when i am clicking on pagination button it gives the error of :

 MethodNotAllowedHttpException in RouteCollection.php line 251:

my form :

``page:generateReport``

<form method="post" target="_blank" action="{{route('MainReport')}}">
    {{csrf_field()}}
//form fields 

<button type="submit">submit</button>
</form>

my route:

Route::post('MainReport','ReportController@MainReporting')->name('MainReport');

my controller:

public function MainReporting(Request $request){
    $this->validate($request,[
        'ToDate'=>'Required',
        'fromDate'=>'Required'
    ]);
    $DataOrderNotSpecial=null;
    $DataOrderSpecial=null;
    if($request->OilStationManazada=='on'){ //condition 
        $DataOrderSpecial=Order::Where(function ($query) use($request){
            $query->whereBetween('order_Date', [$request->fromDate, $request->ToDate]);
        })->Where('subcontract_id','!=',null)->paginate(10);
        $DataOrderNotSpecial=Order::Where(function ($query) use($request){
            $query->whereBetween('order_Date', [$request->fromDate, $request->ToDate]);
        })->Where('subcontract_id','=',null)->paginate(10);
        return view('pages/admin/reporting/MainReporting',compact('DataOrderSpecial','DataOrderSpecial'));
    }
// as you see i am sending form from a page called `` generateReport ``  to another page called `` MainReporting `` has no error on displaying result but only i am pressing the button paginates it gives my the error. please help.

i know i am messing something with pagination. but dont know what is that.