You cannot "open" part .004 directly; you must initiate the process from the first file.
: To successfully extract the content, you must have all preceding parts (e.g., 09.2018.7z.001 , .002 , .003 ) in the same folder. 09.2018.7z.004
: The .004 extension indicates this is exactly the fourth segment in a sequence. You cannot "open" part