Using a meat thermometer?

I'm planning to cook a pork tenderloin for dinner tomorrow. I'll be using a meat thermometer (non digital) to confirm that the tenderloin is fully cooked. I've never used one before and I have a some questions.
What internal temperature should pork tenderloin be cooked to? Do I insert the thermometer at the beginning or end [...]

how long to deep fry 13.5 lb turkey at 300 degrees?

cold and windy outside and can only keep a 300 degree temp. I know it’s 3.5 minutes per pound at 350, so what give it an extra 10 -15 minutes cooking time! Then check inside temp with meat thermometer! Thanks for your help!