I have inherited a site hosted on Pantheon that hasn't been touched (other than content updates) for 5 years. I'm not sure which of these guides apply.

https://docs.pantheon.io/drupal-migration

Terminus shows this as the upstream

Upstream 8a129104-9d37-4082-aaf8-e6f31154644e:[https://github.com/pantheon-systems/drops-8.git](https://github.com/pantheon-systems/drops-8.git)

Which doesn't quite seem to fit any of their scenarios. Anyone have some advice/experience on how to proceed?