Please use below code :

    $objectManager =  \Magento\Framework\App\ObjectManager::getInstance();    
    $storeManager = $objectManager->create("\Magento\Store\Model\StoreManagerInterface");
    $storecode = 'de';
        // get array of stores with storecode as key
        $stores = $storeManager->getStores(true, true);
        // check stores array for this storecode 
        if(isset($stores[$storecode]){
            $store_id = $stores[$storecode]->getId();
        }
    echo $store_id;