In Azure SQL Database, you can configure a single or a pooled database with a long-term backup retention policy (LTR) to automatically retain the database backups in separate Azure Blob storage containers for up to 10 years. You can then recover a database using these backups using the Azure portal or PowerShell.
Configure long-term retention policies :
You can configure SQL Database to retain automated backups for a period longer than the retention period for your service tier.
In the Azure portal, select your SQL server and then click Manage Backups. On the Configure policies tab, select the checkbox for the database on which you want to set or modify long-term backup retention policies. If the checkbox next to the database is not selected, the changes for the policy will not apply to that database.
In the Configure policies pane, select if you want to retain weekly, monthly or yearly backups and specify the retention period for each.
When complete, click Apply.
To view backups and restore from a backup refer to https://docs.microsoft.com/en-us/azure/sql-database/sql-database-long-term-backup-retention-configure