Right-click on part01.rar and select "Extract Here" . The software will automatically pull data from Part 17 and all other volumes to recreate the full game folder.
Most files from this source are password-protected. Try the site URL: otomi-games.com Common Troubleshooting otomi-games.com_B3XZT7E2.part17.rar
If the extractor asks for "Part 18," it means the archive is larger than 17 parts. Check the source page to see if you missed a link. Right-click on part01