The following steps must be performed as part of the migration process:
Step 1: Create the OOTB SDB 2020 database using SDBSetupWizard.exe.
Step 2: Run the pre-migration scripts on SDB 2018/2018 R1 database which needs to be migrated to SDB 2020.
Step 3: Do the Merge & Save of data from source database to target database to complete the migration/upgrade process.