You must have all subsequent parts (part2, part3, etc.) in the same folder to successfully extract the data.
“you always open the first rar and a rar compatible archiver will know to continue along to the next parts.” Reddit · r/SteamDeck · 3 years ago
Multi-part archives can be tricky for new users, but veteran users emphasize that the software handles the complexity for you as long as you start with the first file.
Always run the extracted files through a scanner like VirusTotal to check for malware.
The most basic "review" of a multi-part RAR is whether it extracts correctly.
To evaluate the quality or safety of the content inside, you can perform the following checks: 1. Extraction Success