You can install the Tampermonkey extension from the opera add-ons, but unfortunately you can't get back your installed scripts, which means you'll have to install them all over again.
Not true. Tampermonkey has the built-in ability to export to the cloud and then import from the cloud to another version of Tampermonkey. In fact, I just did that, switching from the Chrome version to the Opera version. Very simple to do.