If you're planning on getting an Xbox One X you probably want to copy over your old console games, settings, or maybe the whole hard drive. Here's a guide how to do just that. The video up there will guide you through the process but depending on what you want to do you'll need an Xbox One external hard drive, an internet connection, or the ability to connect new and old machines via a router. Get all the bits and you'll be able to copy your games from your old Xbox onto the Xbox One X using bulk transfer (via an external hard drive), network transfer (via a router), or even just play games straight off an external HDD.
If you are using an external hard drive though make sure that your HDD has 256GB or more free, is USB 3.0, and formatted to NFTS. As for the rest then watch the video to find out more.