use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Extbase\Configuration\ConfigurationManager;

$typoscript = GeneralUtility::makeInstance(ConfigurationManager::class)->getConfiguration(
    ConfigurationManager::CONFIGURATION_TYPE_FRAMEWORK, 'Myext'
);

$this->centerFolderUid = (int) $typoscript['settings']['centerFolderUid'];