If you can tell me or what type of file you were expecting (e.g., a PDF of a research paper), I can help you figure out how to locate the missing parts or suggest a specific program to open it.
: .7z.004 indicates it is part 4 of a series (e.g., .001, .002, .003, .004, etc.). Unimportant_Rapping_Jackal.7z.004
If you are missing any parts of the set, you will not be able to extract the final paper. If you can tell me or what type