Do you mean a Word document? If so, which version of Word?
If this is Word, are these Chapter Headings in a Header, or just the first line of the first Chapter page?
If you mean Headers, then you can format the headers in the Insert > Headers menu option. For Word 2007 or later you will need to search the menu ribbon for the same Insert options.
If you just mean the first page of each chapter, then try using the Edit > Find/Replace menu option. You may need to use the Advanced options there, and the link below explains a little more about that feature;
Hope that helps.
Word 2003 OS Win 7 Home Premium
I want to search a manuscript that has only numbers for chapter headings and replace this with a double hash mark(##) plus the original number. I can't figure out how this is done. Can someone help me?