If you can to me, I can help you: Identify what part of the image it is. Suggest where the rest of the piece might be found. Reverse image search it to find the complete version. Convert PDF to JPG. Extract images from a PDF - iLovePDF
Look back at the original website, forum post, or gallery where you found this file. Often, individual parts (like 'a', 'b', 'c') are hosted on the same page as a full-size version or a link to a zip file containing all parts.
However, to get the "complete piece" you are likely looking for, here are the best steps to take: