Do you have this warning message in your PowerApps environments?
This environment contains a previous version Common Data Service database. This database and any apps or flows that depend on it must be upgraded to the new Common Data Service for Apps database before March 15, 2019.
If you do, this video might help you out. In this video I show how to delete a previous version of a CDS database.
DO NOT USE THIS APPROACH IF YOU HAVE POWERAPPS IN YOUR ENVIRONMENT THAT USE CDS.
Here’s a link to the MS docs that also describe this process.