Change Theme and Overwrite the content from new theme

There’s a plugin for multiple themes that allows you to display a different theme for each page. I believe it’s called “Multiple Themes.”

A theme is meant to just style your site’s existing content. A theme does not contain any content by itself.

If you want to import some dummy/demo content for a particular theme, please contact that particular theme’s developer for help. Normally, you’ll have to install some companion plugin to import one of the “starter sites” or templates.

What is the new theme you’re trying to set up?

Thanks Jason and George for details.

My requirements are like suppose if on my site theme1 is selected (consider https://websitedemos.net/love-nature-02/ these theme is selected and it has all default content and pages which came along with theme) and then after after using site for few days I want to change theme, let’s say to https://wpastra.com/templates/outdoor-adventure-02/ (Which have some new pages and different layout)

Then by default when we change the theme, it just changes the style and keeps old pages and content only

But suppose if i want import the pages from new theme and overwrite my old pages and content, Is there any way to manually do this?