Migrations from PegaCloud to on-prem don't happen very often. That is why there is very little information available. A migration will depend on your Cloud configuration and your on-prem configuration. If the two are similar, then you could simply try to export and import a RAP. Beyond that, the process becomes more complex depending on database types (Oracle vs Postgres) and any server-side customizations. It is best to contact Pega and start the dialog so that we can give you the best assistance possible.