MACPRO2012
HI I am having trouble with mac book pro 2012 its locked with a disk lock
It sounds like your laptop has a firmware password lock enabled. See this Apple article for details and to confirm this is the screen you are seeing:
https://support.apple.com/en-us/HT204455
If the laptop has a firmware password lock and you don't know the password, then you will need to take the laptop to an Apple Store or an Apple Authorized Service Provider to have them remove the lock. I recommend first contacting the Apple Store or AASP first to confirm what paperwork you need for providing proper proof of purchase and proper ID. Without proper proof of purchase or proper ID Apple will not remove the firmware password lock since it is a security feature.