You can look up your passcode for a limited time.

Hello. It looks like your Mac was locked with Find My Mac. In order to unlock it, you will need to provide the passcode you created while locking the Mac with Find My.

If you can't remember the passcode, you can regain access by using one of the three options below:

• Sign in to iCloud.com/find, then select your Mac from the Devices menu. Select Unlock and follow the steps to verify your identity.
• Unlock your Mac from your iPhone, iPad, iPod touch, or Apple Watch using your device passcode.
• Take your Mac to an Apple Authorized Service Provider along with your proof of purchase.