Search in certain files

Click in the search box and the Search tab will appear, then click on Advanced Options and check File Contents (to enable content searching in non-indexed locations, not really necessary for folders like your Documents but necessary to search in system folders). Next, if you want to search inside a specific folder, navigate to the folder and type the search into the search bar. To list all files of one type, if you know the extension of the file (examples are exe, txt, jpg, png), just type *.exe in the search bar, replacing exe with the file extension. If you want to search the content of multiple files of a certain type (e.g. documents, pictures, notes), you can, in the Search tab, click Kind and select the type, e.g. document., then just type the word you are searching for in its content into the search bar.

What you will do to search for that doc file is click the Search tab, Kind, select Document, then type blablablah into the search box next to the kind:=document
(of course, navigate to the location it may be in before searching)