Unfortunately, the Business Basic subscription does not include the functionality to enable this. You will need the Business Premium plan for this, or the standalone Microsoft 365 Compliance one.
The functionality you are looking for is called Data Loss Prevention as is detailed here: https://learn.microsoft.com/en-us/purview/dlp-learn-about-dlp
At some point, Microsoft provided a basic DLP policy that detects credit cards for all tenants, but this is not the case anymore it seems.