IR Remote

I want to convert two of my cable boxes to respond to IR remote controls (so I can use universal remotes).  The two are an Xfinity XG1-A and an Xfinity PXD01ANI.  They’re several years old.  Neither box has the option to “Enable IR” in the Remote Settings menu.  The questions are:

Can I enable IR remote control on these boxes?  If so, how?  If not, do I need to trade in these boxes for newer ones that can have IR remote control enabled?

What’s the best IR extender to use with these or replacement boxes?