Welcome to the Ranch.
You don't add a row. You add the row data, typically using
DefaultTableModel#addRow(Object[] rowData)
From the API docs for the above method
Adds a row to the end of the model.
If you want to insert add row data, at a specific index, you can use
DefaultTableModel#insertRow(int row,Object[] rowData)
Coming back to your question
For this I need to know the index value of already inserted row.
So how are you building your rows? If you start off with some default data, then the last row would be numberOfRows-1