Koi, I admire you for trying something new. It can be challenging.
Knee pain while bicycling could be due several causes:
Not enough warmup. Give yourself a few miles to warm up muscles and tendons. Go easy in lower gears.
Terrain too steep for your current condition. Take it easy, geadually build up strength and stamina. Find friendly terrain.
Pushing too high a gear. Try to spin 60 to 90 rpm. Use your gears. You wouldn't lug your moto, right?
Poor shoe/cleat alignment. The ball of the foot should be usually be directly over the pedal axle, with the foot roughly parallel to the frame.
Saddle too low or too high.
If you're experiencing knee pain in the front of the knee, typically the saddle is too low. If back of the knee, too high.
If you're getting pain above the knee, my guess is you need to warm up and ride easier gears on relatively flat terrain. You're straining muscle.
Gradually build up time, distance, and difficulty. Don't try to do too much too soon.
Cycling is a great sport/activity/transport. Give yourself credit for venturing out and trying something new. Good on ya!