Because every import and migration from previous system is different, so we might need some custom development to import/migrate from previous system
In order for us to do that, please provide the registrations in a CSV with the format like the following sample
Sample registration import CSV
Please make sure the CSV is with the right format
Once the CSV is in the right format, then go to App admin > Forms > Select the Form > Form Settings > Import CSV > upload the CSV and do the import.