Alarmierung per yaml

Since we upgraded our Grafana to the latest version (from 6.x to 8.5.2) our alerting no longer works. We have seen that the complete alerting has been changed.
Since we have the Grafana running in k8s we need an option to realize this alerting via yaml file. Until now the whole thing worked by having a notifiers.yaml in the StorageAccount.
How can we set up the new system accordingly? Are there also corresponding files that we have to create?

Additional question: Is there a migration option to transfer our previous alarms to the new system?