Not that far away, really. Just spend a few hundred/thousand years to explore the Oort cloud, mining it as you go, and I'm sure once you reach the edge (if there is such a thing) Proxima will be a relatively short jump past that point.
(OK this is pretty far-fetched right now, but it should be possible eventually.)
(OK this is pretty far-fetched right now, but it should be possible eventually.)