How to turn off Activation Lock on iPhone
I set the phone and try to turn on . On my screen its mitigation pops out . iPhone lock to owner
[Re-Titled by Moderator]
Activaiton lock is turned on. If it is activation locked to an old Apple ID of yours and you don't have the credentials anymore and you can provide valid proof of purchase information you can start an Activation Lock support request.
How to remove Activation Lock - Apple Support
If the iPhone is activation locked to an apple id that is not yours there is no way to remove the lock, as activation lock is a theft deterrent system