Right-click only on part01.rar and select "Extract Here" or "Extract to [Folder Name]" .
If you're looking for a gameplay guide for A Plague Tale: Requiem once it's installed, I can help with walkthroughs for specific chapters or puzzle solutions! A.Plague.Tale.Requiem.GOG.part03.rar
The extractor can't find the next part in the sequence. Make sure they are all named identically except for the part number (e.g., don't have one named Game.part01.rar and another Game(1).part02.rar ). Right-click only on part01