When user choose country only then will open to ‘State’ list

Hii all,

I have create a website link is : https://usedsnowboardgear.com/..
in the register page, I need one thing done that when visitors will register their-self and select the country option.. then only i need states list open.. state list should not be visible or select before visitors choose the country, it should be selected after select the country option.. also i need the state list according to the country selection.. like if i choose USA then only USA states will be selected or appear.. Other countries states will not be appear.

Please help MARK..!

Thanks in Advance.