It is very easy to search all of your files at once using the built-in search feature on your computer.
Click the start button in the lower left-hand corner of the screen, then click "This PC":
Make sure "This PC" is listed in the bar at the top of the window, then type your search term in the box located at the top right of the window > Press the enter key to begin the search:
It may take several minutes for the search to complete depending on how many files you have.
The search results will appear: