You can't.
The DataReport is a custom view which is 'rendered' upon presentation but
has no storage other than the initial data structure and rules on how to
display it. Similar to rendering a presentation on a Form using PRINT
statements.
You can however export a DataReport as text or html to another viewer/editor
(Notepad, Word, WordPad, etc.) and use that utility's facilities for
searching, etc.
-ralph