This policy identifies AWS RDS instances which are not encrypted. Amazon Relational Database Service (Amazon RDS) is a web service that makes it easier to set up and manage databases. Amazon allows customers to turn on encryption for RDS which is recommended for compliance and security reasons.
Amazon RDS instance can only be encrypted at the time of DB instance creation. So to resolve this alert, create a new DB instance with encryption and then migrate all required DB instance data from the reported DB instance to this newly created DB instance.
To create RDS DB instance with encryption, follow the instructions mentioned in below reference link based on your Database vendor:.