It is suggested to use Upgrade Checker Utility, before initiating the upgrade. You can use the upgrade checker utility to check MySQL 5.7 server instances for compatibility errors and issues for upgrading.
Create a dump of the OLD_CB codeBeamer MySQL schema: Export dump
Shutdown OLD_CB instance forever.
Setup a new MySQL instance as an independent service (you can also use an already existing shared MySQL 8.0 or higher instance) and prepare the new codeBeamer schema according to Preparing the MySQL Database for Installation.
Import the dump into the new database schema: Import dump