Please refer my previous article to learn more about SharePoint Designer 2013 Workflows.
In this blog you will see how to use “Extract Substring from End of String" action in SharePoint Designer 2013.
Description:
Here, I will copy a specified number of characters starting from the end of a string and store the output in a variable.
In this example, I have copied last 5 characters from end of “Name” field and stored it in a “ExtractSubstring” string variable and updated the current item “Notes” field to display the output string.
Workflow Design:
Result: