If you’d like to know which version of WordPress you are using, go to your WordPress dashboard (www.yourdomain.com/wp-admin), and scroll down to the bottom right of the screen, and you will see the Version, e.g: Version 5.3.

If you have administration rights, and you’re using the free WordPress.org, you can visit dashboard (www.yourdomain.com/wp-admin) > Dashboard > Updates, and update your WordPress software.