You need software such as WinRAR (Windows), 7-Zip (Windows/Linux), or The Unarchiver (macOS) to extract the file, provided you have all the parts in the same folder [1, 2].

If you are missing other parts, the archive cannot be restored [2]. To get a more tailored answer, I'd need to know:

did you download this file from? (e.g., a specific website, email attachment?) Are you trying to repair a broken download or just open it?

Such files are almost exclusively used for sharing large datasets, software, or media, broken down into smaller, manageable chunks [1].

Because part files are often used to distribute large, unauthorized, or pirated content, they frequently appear on file-sharing sites. It is highly recommended to scan any RAR file with antivirus software before attempting to open it [2].

This helps me guide you on the next steps for your specific situation.