With the release of RHEL9 the RHCSA and RHCE training & certification content has been revised to keep in pace with the technology changes and updates.
If your certification on RHEL8 is still current, you need to just pass EX294 to upgrade to RHCE in RHEL9
If your certification is not current, then you need to pass EX200 (RHCSA on RHEL9) and also pass EX294 exam to upgrade to RHCE on RHEL9