How to show updated on date on blog posts

Hi there,

are you using the Block Editor on that site ?

I have no idea. What is block editor? I am using a regular WP editor.

Any new install of WP would use the block editor.
Does it look like the screenshots shown here:

https://wordpress.org/support/article/wordpress-editor/

That's right. I am using block editor. I am not using classic editor or any other editing plugin.

What should I do to show last updated on my updated posts?

Try this CSS:

.posted-on .published:before {
    content: "Published on: ";
}

.posted-on .updated {
    display: inline-block;
}

.posted-on .updated:before {
    content: "Last updated: ";
}

.posted-on .updated + .published {
    display: none;
}

Thank you, it's working.

You are welcome :)