By default, WordPress uses a URL structure that doesn't include file extensions like .html. Nevertheless, it is worth considering the potential advantages and disadvantages of deviating from this rule and including extensions into the permalinks.
Many top-ranking websites on search engines may include links that lack the .html and.php extensions. In most cases, adding them to your new URLs is not necessary from an SEO standpoint.
Although this is a general rule, there are certain situations when it may be beneficial. A good example of this is when you have switched your store from Magento to WooCommerce or plan to do so soon.