Open the extracted folder and run setup_medieval_dynasty_xxxx.exe . Follow the GOG installer prompts. Play the game directly from the desktop shortcut.
Right-click on part01.rar and select using WinRAR or 7-Zip . It will automatically pull data from all other parts (including part 09). Medieval Dynasty GOG.part09.rar
It looks like you’re trying to assemble or share a multi-part archive for the GOG version of . Since you specifically mentioned part09.rar , Medieval Dynasty (vX.X.X.X) – GOG DRM-Free Medieval Dynasty (vX.X.X.X) – GOG DRM-Free