use TYPO3\CMS\Core\Utility\GeneralUtility;
use TYPO3\CMS\Extbase\Configuration\ConfigurationManagerInterface;
use TYPO3\CMS\Extbase\Object\ObjectManager;


$om = GeneralUtility::makeInstance(ObjectManager::class);
$ts = $om->get(ConfigurationManagerInterface::class)->getConfiguration(
    ConfigurationManagerInterface::CONFIGURATION_TYPE_FULL_TYPOSCRIPT
);
$mydata = $ts['plugin.']['tx_myext.']['settings.']['something'];