In a multi-part set, all parts (Part 1, Part 2, etc.) must be in the same folder before you can extract them. You generally only need to right-click Part 1 and select "Extract Here" to unpack the entire game.
If you are encountering this file while attempting to install or play, here are the most relevant details: AssassinsCreedValhalla.part5.rar
This stage usually covers the transition from Norway to England, where Eivor and the Raven Clan establish their settlement, Ravensthorpe . In a multi-part set, all parts (Part 1, Part 2, etc