One UI 6

[imBilalQamar]

Where is the option in Lockscreen pin "Confirm without tap Ok"

[user9992112]

At the time of setting up the screen lock, there is a check box on the same screen.

[Kashifasghar]

But OK thing is fine for security purposes, I myself have OK button on lockscreen

[HasanAskari]

Settings app -> Lock screen -> Screen lock type -> Enter your pin -> enter new PIN -> re-type your new PIN to use as the "new" pin, and tick the "Confirm PIN without tapping OK" checkbox. Continue and re-type your pin again. It'll auto confirm, and then your lock screen will automatically unlock once you enter the correct PIN. 

You have to change your pin