Use the 7-Zip official tool to "Test" the archive. If .004 is corrupted, the extraction will fail even if you have the other parts.
Ensure you have C54.7z.001 through at least C54.7z.004 .
If the archive is encrypted, the password is often required at the beginning of the extraction from the first part.
If you attempt to open .004 without .001 , your extraction software will report an "Unexpected end of data" or "Can't open file" error.