i want to know how to enable usb port in mac

Yes, they should be on by default, as healthy one says. But a word of warning. Unless you are experienced with the innards of a Mac, I would not go into Terminal. A false move there can make a lot of trouble. If you have an Authorised Apple re-seller or retail store nearby take it in to the genius bar. That is free.

The USB ports should be 'on' by default. So if they are not working, then click the APPLE icon in the upper left corner, select 'About This Mac' then from the pop-up window select 'More Info' which will get you to the various hardware components. Look at your USB device(s).

For the 'Terminal' commands, those are standard Unix. So just do an Internet search on Unix/Linux commands and you should be fine.

Hope that helps.

USB information:

https://support.apple.com/en-us/HT204377