Delete all duplicate post

I am running several WP blogs each has some hundreds posts. I just realized that some how my blog auto generate duplicate posts for certain articles

For example, when i wrote a new post like this

mydomain.com/this-is-my-post

Then, there may be some posts like this

mydomain.com/this-is-my-post-2
mydomain.com/this-is-my-post-3

These post has same content with mydomain.com/this-is-my-post

Question:
Is there any way to remove these duplicate post easily? I don’t want to manually delete individual posts since it is very painstaking

I’m thinking that maybe we can change something in htaccess file to redirect all the extra post to the original post with some line of codes. But i don’t know how to do it.

Could anyone please help me?

Thank you!