Equivalent laravel relationship query for this join

this is my query

$personnel_info = \DB::table('assigns AS a')
        ->join('boxes AS b','b.id','=', 'a.box_id')
        ->join('positions AS p','p.id','=', 'b.position_id')
        ->select('a.id','b.id AS box_id','p.id as position_id','p.title','a.status','a.end_date')
        ->where('a.personnel_id','=',$personnel_id)
        ->get();

and this realtionship for boxes:

    class Boxes extends Model
{
    public function position()
    {
        return $this->belongsTo('Positions');
    }

    public function assign()
    {
        return $this->hasOne('Assigns', 'box_id');
    }
}

how to use eloquent query(also realtionship) for replace DB facade query? i want select some field for tables. tnx

via Rohullah Rajaee Rad