Once you have Xbox 360 games you can play these games on PC using an Xbox emulator. This method is better than downloading an ISO file which has a lesser probability of running the game successfully on an Emulator. If you already own Xbox 360 games CDs then you can extract the game manually to an external drive.

You can also buy games if it is paid from the Store.

In Microsoft Store, search for the Xbox 360 game you want to download.Search for Microsoft Store and Open it, You can also open Microsoft Store from the all Apps section.How to Download Xbox 360 Games on PC From Microsoft Store: Steps to Play Xbox 360 Games on PC using Xenia.How to Download Xenia Xbox 360 Emulator for PC.Minimum System Requirements to Play Xbox 360 Games on PC.