To successfully extract the contents, you must download all associated parts (part1, part2, etc.) and place them in the same folder WinRAR Help.
What are you expecting inside? (e.g., a game mod, software)
Use software like WinRAR or 7-Zip to open only the first file ( .part1.rar ). The software will automatically detect and join the subsequent parts ( .part2.rar , etc.) to extract the files.