JavaScript dialog delete error in Laravel 9

I want to create a confirmation dialog in JavaScript before deleting an item.

My JavaScript code

function confirmerSuppression() {
        var confirmation = confirm("Êtes-vous sûr de vouloir supprimer cet élément ?");

        if (confirmation) {
            window.location.href = '/tiers.destroy/' + id; // 
        } else {
            alert("Suppression annulée !");
        }
    }

Code for my delete button

<form action="{{route('tiers.destroy', $tiers->id)}}" method="POST">
@csrf  
<button onclick="confirmerSuppression()" class="btn btn-danger w-100 type="submit">DELETE</button>                                 
</form>

My route:

Route::post('/tiers/details/{id}', [AppHttpControllerstiersController::class, 'destroy'])->name('tiers.destroy');

My controller :

public function destroy($id)
    {
        Tier::where("id","=",$id)->delete();
        return redirect()->route('prospects.liste')->with("success","Tier supprimée avec succès.");
    }

When I click on the DELETE button the dialog appears and when I click on Cancel it deletes the element the same when I click on Yes.

Anyone have an idea please.