You could possibly try using this FAQ Forgotten Pin. If it does not resolve your issue, you can always contact Technical Support. Via Phone/Online Chat being most expedient.. https://service.mcafee.com/webportal/cp/home/contact
All the Best,
I would request you to have a look at this kb article mentioned below , if it doesn't help please contact McAfee Mobile Support for unlocking the device.
"The device is locked and you have forgotten your Mobile Security six-digit PIN" : Forgotten Pin.
Mcafee Mobile Support: