Sounds about right, but you’ll have to pay to upgrade your Elements license to at least Artist, and to do that, you’ll also have to buy a USB eLicenser; seems a bit unfair to me. Kudos for perisistence in trying to revive the old stuff though!
Once upon a time, in the dark days when Steinberg were owned by Pinnacle, there was a version of Cubase SE (a cut-down equivalent of SX, or “SX1”) which did not use the Synchrosoft system, just a serial number that you could use to activate the software, even offline. That never made it past Windows XP, however it just might run in a Windows XP VM well enough to convert files.
Of course, if Steinberg were to publish the format of the now obsolete .ALL, .SNG and .PRT files, perhaps the community could create a proper conversion utility.