Could someone please explain points.com for me? I'm interested in making my American and Delta miles magically turn into United miles, and I can't quite understand how that happens and whether it would cost me anything.

At this point, the 40,000 American miles are phantom, as they expired some time ago. But with a little effort, I can get them reinstated; I'm trying to decide if it's worth the cost of a non-United ticket to do it.

Thank you!