You need a file archiver tool. Common options include: WinRAR (The official tool for .rar files) 7-Zip (Free and open-source) WinZip
Are you receiving an error when trying to extract the file, or are you missing the other parts of the archive? How to Extract Part .RAR Files (Full Guide) sc24265-ETSv146213s.part1.rar
Note: You only need to extract the first part ( part1 ); the software will automatically join the subsequent parts. You need a file archiver tool