how can I add more USB ports to my Mac mine

This is done by purchasing an external USB bridge and connecting it to your Mac. They come in various sizes. so you can get one to suit your needs. Some bridges come with an external power source and others have none. I only recommend the powered bridges. Most external devices will work fine being connected to them. Some external non powered devices will not work on a non powered bridge and that is why they instruct you to only connect them directly to the computer. Most bridges sold today should work just fine.

Glad to be of service.