Downgrade plugin – i got the backup files

i accidentally updated a plugin called Striper.

Before it had a perfect layout and now its all back to the ugly version and in a language (english) that is not appropriate for my website.

how do I downgrade to the old verison?

i got the back up of the file from yesterday where I have the Striper folder in my WP-content folder from the FTP backup I made yesterday.

How do I get it back to normal?

Thanks