Use a tool like WinRAR or 7-Zip . You only need to right-click on part01.rar and select "Extract Here." The software will automatically "stitch" Part 25 and all other pieces back together into the original full-sized file.
Place all numbered parts in the exact same folder on your computer. Call.of.Duty.Modern.Warfare.part25.rar
It looks like you’ve come across a specific part of a —essentially a large file (likely a game installer) that has been chopped into smaller pieces for easier downloading or sharing. Use a tool like WinRAR or 7-Zip