where does earbud be connected to iphone

I believe this was the first model that the headphone jack was removed..

So you would need to use the earbuds that came with the phone.. or find/buy some that will connect to the lightning port.

There is also an adapter you can buy

Lightning to 3.5 mm Headphone Jack Adapter

I think this adapter may have even come with that first generation where the port was removed.

of course, you could go wireless and find some Bluetooth headphones as well.