Hi there!

Thanks for your query.

You may use the following code snippet in your custom CSS:

.blog .article-list .article.type-intro {
    display: flex;
    flex-direction: column;
}
.blog .article-list .article .article-body {
    order: 1;
}

Note: Path towards custom CSS(Joomla 3): Extensions>Templates>Styles> Click on your current default template name then choose Template Options. Then find custom CSS within the custom code.

Best Regards