If your extraction fails specifically at part08.rar , that specific file is likely corrupted. You should re-download only that segment rather than the entire library.
Ensure the filename matches the rest of the set exactly. If part01 is named differently than part08 , the extraction software will lose the "link" and report a "Missing Volume" error. Microsoft_Flight_Simulator-HOODLUM.part08.rar
Once extracted, ensure your system meets the baseline for the 2020 release: Intel i5-4460 or Ryzen 3 1200 GPU: NVIDIA GTX 770 or Radeon RX 570 If your extraction fails specifically at part08