Hi Farah abid,
you can do this by parsing through repeating table rows in a Nintex workflow on item update and create action. There is also a custom wsp available in the community site if this is something repeatedly required in your site.
To do in Nintex workflow way, all you have to do is connect the repeating section to mulitline text field in the list for ease of access. use regular expression to get <Item> nodes to collection and loop through them.
You have to name each of your controls in the repeating table for being able to use QueryXML operation that is very handy here
In the end your workflow would look like this
output would look like this
For now I am attaching a sample Nintex form and workflow which can help you through.
I hope this helps.
and the 3rd approach might be repeating section field type.
note however that this is not native sharepoint nor nintex field type and you need to install 3rd party add-in to the sharepoint to have it available
have a look here for details - Displaying Repeating Section Data in List Views, The Easy Way!