A highly recommended, lightweight tool available at 7-Zip.org .
Select 7-Zip > Extract Here or Extract to "FS_10DStfnftum7u" . In WinRAR: Select Extract Here .
You only need to interact with the first file in the sequence. Right-click on FS_10DStfnftum7u.part1.rar . Choose "Extract":
If the archive is encrypted, you must enter the password provided by the original uploader.