You cannot extract the contents from .001 alone. You must have all parts of the archive (001, 002, etc.) in the same folder before beginning extraction.
It is recommended to use the 7-Zip utility for Windows, or apps like Unzip One or RAR Lab for other platforms. How to Extract
Ensure you have KIA.7z.001 , KIA.7z.002 , etc., all located in the same directory.
Choose "Extract here" or "Extract to..." in the 7-Zip menu. The software will automatically combine the parts and extract the final file. To give you a better write-up, I need to know:
of this file (e.g., is it firmware, a game, or a document)? Are you experiencing an error trying to open it? How to Extract .7z.001 files - Microsoft Q&A
.7z is a high-compression archive format developed by 7-Zip.