Tenderloins are really easy to cook. So don’t worry! I own one of these thermometers and you can set the temp that you want the meat to reach and it will alert you when it reaches that temperature.
https://meater.com/ So that makes it really fool proof. But even without it, it’s easy to cook. My advice, err on the side of less done. Once you make it well done, there is no going back. Your ends of the tenderloin will be more done and you can have a slice from the inside that is more pink. We make our tenderloin with a sour cream horseradish sauce that is easy and delicious. GL