Many cheaper Arduino clones, like this Arduino Nano from Banggood, use a CH340G USB controller in order to bring down the cost.
The Mac Os does not come with a driver for this chip. As a result, you will not see a USB port in the Arduino IDE when you connect such boards.
You will need to install the appropriate driver on your Mac.
This should help you: https://github.com/adrianmihalko/ch340g-ch34g-ch34x-mac-os-x-driver