I don’t have lock unlock option in settings of my iPad Pro

Thanks for your explanation (it was not that easy to understand (remotely) your needs reading your original question).

After reading this support article:--> Use the Smart Folio or Smart Cover with your iPad - Apple Support

if you're sure you're using the correct smart cover, compatible with your iPad model, AND if you don't see the lock-unlock option in Settings>Display&Brightness, make an appointment and have your device inspected at an Apple Store or AASP (Apple Authorized Service Provider) among this list:--> Apple – Location Selector

After checking it out, they'll give you all the available options.

Regards

Giulio

If you're talking about the passcode, go to:

Settings>Face ID & Passcode... (iPad with Face ID)

or, Settings>Touch ID & Passcode... (iPad with Touch ID)

If you mean something different, please better specify your needs.

Regards

GIulio