Find a word in a file

If you mean you want to search for which, if any, files contain a word, one option is to use Spotlight. Click the magnifying glass icon on the menu bar or use command spacebar to open it. Also see: Search with Spotlight on Mac - Apple Support

Note that the results will contain files as well as other results -- see the above link for information.

If you are interested in finding a word using Spotlight, particularly in a Pages document, you have some options to narrow the search results. If you want to find a word in a Pages document created after a certain date, or in the second example, last opened in a date range. The third reveals Pages documents with a Baskerville font used in them:

kind:pages created:>07/01/2022 word
kind:pages date:>07/01/2022-09/30/2022 "two words or more"
kind:pages font:basker



You can change pages to Word (MS Word) or PDF if you want to narrow the search to those document types only.