To retain a user's Microsoft 365 audit logs for 10 years, you need the 10-Year Audit Log Retention add-on license, which must be assigned to that specific user in addition to an existing Microsoft 365 E5 license or Microsoft 365 E5 Compliance add-on license.
Required Licenses & Components
Microsoft 365 E5 License: This is the base license that enables longer-term retention.
10-Year Audit Log Retention Add-on: This is a separate license that must be purchased and assigned to the specific user whose audit logs you need to retain for 10 years.
Reference:
https://learn.microsoft.com/en-us/purview/audit-log-retention-policies