Activation lock

try

https://iforgot.apple.com/password/verify/appleid

otherwise

https://www.apple.com/retail/geniusbar/ and or https://getsupport.apple.com/

Visit an Apple Store.

RaheelJavaid wrote:

Visit an Apple Store.

...or follow Rudegar's advice first to retrieve the ID online without having to make a journey.

my iphone is stopped suddenly

Then you should start your own thread and post as many details as possible about the situation.