Multiple external hard drives - how select to which one to move?

If you have enough space on your external HDD, copy everything there from inside the Xbox.

Make sure your saved games are in the cloud. Then on the new one just set your default drive to the external

Open Settings on the Xbox One.

Open the System tab.

Select Storage.

Select the internal drive.

Select Transfer.

Select items you plan to transfer. If moving all items, choose Select all.

Choose Copy selected to copy the items between drives.

To move the items, select Move.

Choose the Ext. drive.

Press Copy or Move to transfer.

After transferring your games to an external hard drive, plug it into the new Xbox One.

Stored should appear in your library.

To transfer games from the internal hard drive to an external hard drive on an Xbox Series S or X, navigate to "My games & apps", select the game you want to transfer, choose "Move or Copy", then select the external drive as the destination and confirm.

You are using transfer, which is to move the contents of your internal hard drive to the external hard drive instead of copying, you do not need to manually delete the contents of the internal hard drive (because they are already on the external hard drive).

Hello Vash,

Thank you for keeping us updated. There are some instances in which games on an external hard drive do not receive updates. We recommend moving around some of the games on the internal and external hard drives. Since your internal hard drive is full, you
can move some of them to the external hard drive. Once the internal hard drive has some extra space, we suggest moving some of the games from the external hard drive to the internal. Check to see if those games require any updates. Be sure to let us know the
results!

It's possible that the file on your external hard drive is corrupted which means that you may have trouble moving it. You may need to reformat the external hard drive in this case.