What are the upgrade steps to get from 188.8.131.52 to the latest version?
Also, just for my information, which version is the first to be compatible with PHP 7.2? Dreamhost just upgraded to that and my site went blank with an HTTP error 500.
Beyond that, its more of a content migration to a new site rather than an upgrade. You would need to install the exporter, export the site content as xml, then import that to a fresh install of the latest 8.5.2. But even if the content imports, there is a lot more to it.
Bear in mind that addons and themes available for 5.6 may not be available for 5.7 or 8.x.
If your site is fairly static without any big changes on the horizon, get to 184.108.40.206 and leave it there. If you have plans for onward development, then start a new site in 8.5.2 and migrate what content you need to continue.
For the future: is there a "how to" resource for how to set up a new version of Concrete5 so that I can test a move to the latest version? Is it just a matter of extracting the Concrete5 files to a separate root folder on the server, or are the resources shared across different sites under my server account?