TYPO3 10+

In Configuration/Extbase/Persistence/Classes.php

See https://docs.typo3.org/c/typo3/cms-core/10.4/en-us/Changelog/10.0/Breaking-87623-ReplaceConfigpersistenceclassesTyposcriptConfiguration.html

TYPO3 7-9

via TypoScript:

config.tx_extbase {
    persistence {
        classes {
            Vendor\Extension\Domain\Model\Teammember {
                mapping {
                    tableName = tx_extension_teammember
                }
            }
        }
    }
}