Large datasets are often split into smaller "volumes" or "pieces" (e.g., part1, part2) for easier uploading/downloading.

If FOR20-40.rar is part of a series (e.g., if there are files like .001, .002, or .part1), ensure all related pieces are in the same folder.

Use tools like WinRAR (the official tool), 7-Zip (free and open-source), or WinZip .