The following article will help you to redirect your website from HTTP to HTTPS in the Plesk panel.
Step 1: Log in to the Plesk Panel.
Step 2: Click on the Website&domains.

Step 3: Click on the Hosting Settings.

Step 4: Under the SSL/TLS support, tick on SSL/TLS support and Permanent SEO-safe 301 redirect from HTTP to HTTPS checkboxes.
Also, select the valid certificate from the certificate list that you want to use for your website. Then click OK to save the changes.

Now your websites will use the secure HTTPS protocol, and all the users will be redirected to HTTPS even if they type the URL with HTTP.