const students = [
  {name: "a", id: "4832"},
  {name: "b", id: "4354543"},
]

const idTemplate = (rowData) => {
    return students.findIndex(x => x.id === rowData.id)
}

<DataTable value={students}>
  <Column header="#" body={idTemplate}></Column>
  <Column field="name" header="Name"></Column>
</DataTable>