Thank you. But this will not help.

Applying numbering can be done but that will never become part of the heading when I try to use, say Find and Replace, or import the document to another software. The numbering is Field Codes in place. I want the heading's text to be replaced with numbers like 10001, 10002, and so on.

Also, * and ^p doesn't work. Note that I want to change the text in headings only. Can you suggest something else with these details. Note that I want to do this for all heading levels in the document.