Magento 2 product image custom resize

Question

I have created custom attribute for featured product and fetched the product collection using object manager.

 <?php 
 $objectManager =  \Magento\Framework\App\ObjectManager::getInstance();        
 $priceHelper = $objectManager->create('Magento\Framework\Pricing\Helper\Data');

  $collection = $objectManager->create('\Magento\Catalog\Model\ResourceModel\Product\Collection')
  ->addAttributeToSelect('*')
  ->addAttributeToFilter('newest_product',['eq'=>1])
  ->addAttributeToFilter('status',\Magento\Catalog\Model\Product\Attribute\Source\Status::STATUS_ENABLED)
  ->load();

   foreach ($collection as $product) 
  {
    $pdata = $product->getData();   
    $store = $objectManager->get('Magento\Store\Model\StoreManagerInterface')->getStore();
    $imageUrl = $store->getBaseUrl(\Magento\Framework\UrlInterface::URL_TYPE_MEDIA) . 'catalog/product' . $product->getImage();

 }
 ?>

Here $imageUrl Returns the full image of the Product while I want the image of 300X400

I am trying to get the 300X400 size image in $imageurl code but not sure how to get the resized image. If you see the code, I have not used the helper method.

Need help to resize the product image to 300X400.

Any help would be appreciated.