Please refer my previous article to learn more about SharePoint Designer 2013 Workflows.
In this blog you will see how to use “Extract Substring of String from Index with Length “action in SharePoint Designer 2013.
Description:
Copies out a substring comprising a specified number of characters, starting at a specified index in the string, and places the value in a variable.
Note: The index value in Microsoft SharePoint Designer 2013 is zero-based.
In this example, I have copied a substring starting at a specified index 3 for a specified number of characters from “Name” field and storing it in a “ExtractSubstring” string variable and updating the current item “Notes” field to display the output string.
Workflow Design:
Result: