error during checkout

[farrum]

Hi,
I implemented the module. Then created a module on mage2gen.com for additional customer address fields.
got this error on checkout page

Fatal error: Uncaught Error: Class 'Experius\ExtraCheckoutAddressFields\Helper\Data' not found in /home/customer/www/stage.orgmanics.com/public_html/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php:121 Stack trace: #0 /home/customer/www/stage.orgmanics.com/public_html/vendor/magento/framework/ObjectManager/Factory/Compiled.php(108): Magento\Framework\ObjectManager\Factory\AbstractFactory->createObject('Experius\ExtraC...', Array) #1 /home/customer/www/stage.orgmanics.com/public_html/vendor/magento/framework/ObjectManager/Factory/Compiled.php(150): Magento\Framework\ObjectManager\Factory\Compiled->create('Experius\ExtraC...') #2 /home/customer/www/stage.orgmanics.com/public_html/vendor/magento/framework/ObjectManager/Factory/Compiled.php(79): Magento\Framework\ObjectManager\Factory\Compiled->get('Experius\ExtraC...') #3 /home/customer/www/stage.orgmanics.com/public_html/vendor/magento/framework/ObjectManager/Factory/Compiled.php(150): Magento\Framework\ObjectManager\Factory\Compiled->create('Experius\ in /home/customer/www/stage.orgmanics.com/public_html/vendor/magento/framework/ObjectManager/Factory/AbstractFactory.php on line 121

please help