Questions about the datagridview

I'mtryingtousethecodebutIcannotfigureoutwhyIcannotputaStringinthecolumnsbecauseI'vebeensettointandIcannotchangethat.

publicstaticDataTablefillDataTable(stringquery){using(OdbcConnectionconexao=Conexao.CreateConnection()){OdbcCommandcomando=newOdbcCommand(query,conexao);conexao.Open();DataTabledt=newDataTable();try{dt.Load(comando.ExecuteReader());for(inti=0;i<dt.Rows.Count;i++){Stringquery2="SELECT * FROM tbTipoConta WHERE idTipoConta = "+dt.Rows[i][1];
                        List<TipoDeConta> t = CRUD_TipoDeConta.consultaTipoConta(query2);
                        dt.Rows[i][1]= t[0].nomeTipoDeConta;
                    }
                }
                catch (Exception e)
                {

                    throw;
                }

                return dt;
            }
        }