Based on a search of available information, there is no direct, recognized, or legitimate software, document, or archive named "derjrefkio.7z" known to public records.
If you are asking how to open a 7z file in general, it is a high-compression file format. Here is how to handle it: derjrefkio.7z
the file with an updated antivirus program (like Windows Defender, Malwarebytes, etc.) before attempting to open it. General Guide to .7z Files Based on a search of available information, there