: Use an extraction tool like 7-Zip or WinRAR . You only need to right-click on part1.rar and select "Extract" to begin the process for the entire set.
: The "v08g" in your filename indicates a specific update version from GOG.com . Ensure all parts match this version string exactly to avoid errors. Streets.of.Rage.4.v08g-GOG.part2.rar
Do you have of this specific set, or are you seeing an error message when trying to extract? : Use an extraction tool like 7-Zip or WinRAR