string change show more posts

You can change it by selecting the post as pagination type and also enable post pagination. After enabling it you can find the Next-Previous option in post pagination type.

For reference please follow the below documentation:
https://ampforwp.com/tutorials/article/how-to-enable-post-pagination-in-single-page/

I am asking about the blog home page navigation “show more posts” and “show previous posts” not about single post.

Have tried through po edit also but nothing works. Pls help.

Sorry for the wrong observation. If you want to change the ‘show more posts’ and ‘show previous posts’ text for this you need to follow the below steps:

You will find this option in the WordPress Dashboard -> Navigate to AMP Option panel -> Settings -> Translation Panel -> Edit ‘Show more Posts’ and ‘Show previous Posts’ text after that click on the “Save Changes” button.

Ref screenshot: https://prnt.sc/11vhzyo