How to Get Index Value of an Element of Nested Table

I create a nested table, then populated this nested table.

I have some question on above table which are following :

  1. now i want to get index value of a particular element of nested table

like what is the index value of JONES who is in ENAME Column of EMP_NTAB Nested table.

  1. I need to update the Job of JONES Only.

Note - File is attached
01.txt (822 Bytes)