I got unserialize error at offset 0 of 115

I am fetch serialize data from mysql DB and try to unserialize them for further use, however, I got error at offset 0 of 115 bytes

Data I am trying to unserialize :

'a:2:{i:0;a:2:{i:0;i:1;i:1;s:2:"38";}i:1;a:2:{i:0;i:2;i:1;s:2:"39";}}'

And this is my code:

  public function retrival(){

$warehouse_data  =DB::table('initial')->select('variable1')
  ->where('option','=',8)
  ->get();


$decode_data=unserialize($warehouse_data);


}

via Chebli Mohamed