Try this:
<!DOCTYPE html>
<html>
<head>
<script src="http://ajax.googleapis.com/ajax/libs/jquery/1.10.2/jquery.min.js">
</script>
<script>
$(document).ready(function(){
$("#btn").click(function(){
var rownumber = $('#txt').val();
var $selector = $('table#tb1 tr:nth-child('+rownumber+')');
$('#placeholder').html($selector.html());
});
});
</script>
</head>
<body>
Enter row number: <input type='text' id='txt' />
<p id="placeholder"></p>
<button type="button" id='btn'>Click Me!</button>
<table id="tb1">
<tr id="tr1">
<td>Id</td>
<td>Name</td>
<td>Email</td>
</tr>
<tr>
<td>1</td>
<td>XYZ</td>
<td>A@gmail.com</td>
</tr>
<tr>
<td>
<table>
<tr><td></td></tr>
<tr><td></td></tr>
<tr><td></td></tr>
</table>
</td>
<td>
</td>
<td>
</td>
</tr>
<tr>
<td>2<td>
<td>suresh<td>
<td>Karthi<td>
<tr>
</table>
</body>
</html>