On/Off button is of extreme right hand of the top row of the keyboard. However, the actual means to shut down a Mac is under the Black Apple Menu/Shut Down...
To use the power button, press and hold the power button for ten seconds and it will force the MacBook to shut down.
Keep in mind the MacBook is designed to not be shut off, but rather to go to sleep mode. The Mac's underlying Unix™ operating system does housekeeping when it has been left untouched for several hours. It is actually best practice to not shut down a Mac.
That new-shaped plug is a USB-C port that also doubles as a high-speed Thunderbolt 3 port. It doesn't care which way the jack is oriented when you plug in. it is far more than a mere USB port as it has a multitude of signals that can be sent through it at high-speed.
There are several good "docking" solution adapters for that port that include power pass through, multiple USB-A ports, HDMI, media card reader, audio in-out, mini-video, Thunderbolt, etc. These price out from $30 to $80. What's nice is you can keep all the cables plugged into the dock and then just plug the dock into the MacBook using the single USB-C/Thunderbolt jack when you get to your desk.
If you don't need all of that, there are individual adaptors for each of those ports for around $5 to $10.