I have added this code in the Code Snippets
add_filter( 'generate_post_date_show_updated_only', '__return_true' );
And this one, too, in the CSS
/*New Code for Updated Date*/
.posted-on .updated {
display: inline-block;
}
.posted-on .updated + .entry-date {
display: none;
}
.posted-on .updated:before {
content: "Last Updated on ";
font-weight: bold;
}
.entry-header .entry-meta > *:not(:last-child):after {
content: " | ";
}
/*End Code*/
But still it is not working