If you have found a link containing these keywords and it isn't working, it is likely due to one of three things:
This likely refers to a mobile subdomain (m.) for a file-sharing site. "Upfiles" is a common generic name for various cloud storage services used to host images and documents.
This indicates the file format (JPEG) and suggests the user is looking for a functional ("working") direct link to the image. Why Do These Links Often Fail?
Some "upfile" servers check where the request is coming from. If you paste the link directly into a browser instead of clicking it from the host site, it may fail.