I need passcode for Mac Pro to unlock. I didn’t lock this mac

The passcode will be the code that you created when you set up the Mac. If you didn't create the code and you don't know it, as long as you know the code that was used when you set up the Apple ID that it is assigned to. If you know that then you'll be able to unlock it either by following the instructions here or restarting the computer to factory default. If you don't know the Apple ID then you are going to have a paperweight as there isn't a way past the Activation Lock as it is designed to keep unauthorized users from getting access to the computer. Would be pretty useless if someone could just get past it.

Hi CebuanaMontana,

Welcome to the Apple community where some of us do our best to help each other.

Apple has a support pages that can help you.

I forgot my password:

https://iforgot.apple.com/password/verify/appleid?r=1&language=US-EN

If you change your Apple ID or password lately you may need to update your sign-in information with any Apple services that you're using. The support page below can help in this situation:

What to do after you change your Apple ID or password:

https://support.apple.com/en-au/HT204071

If you forgot your Apple ID password

https://support.apple.com/en-au/HT201487

On the left above your question on this page, there is a link to a "Related Article" you can look at, if it is useful.

Cheers :-)