First, if McAfee won't provide an uninstall code, the only advice I can provide is to back up files and data stored locally and perform a wipe and reset from the downloadable recovery image. Go to https://support.microsoft.com/en-us/surfacerecoveryimage
(with a different Windows computer if yours is not working properly)
and download a recovery image for your Surface. You will need a 16GB or 32GB USB stick (also called a flash drive) formatted FAT32 (use a Windows computer). You can't use an actual external USB hard drive for this and don't use anything larger than a 32 GB USB stick. Best to purchase and use a new, previously unused USB stick for this. Use FULL format and not quick format and give the volume a name like surfboot. Unzip/extract the recovery zip to the root of the formatted USB stick.
There are full instructions and a video at https://support.microsoft.com/en-us/help/4023512/surface-creating-and-using-a-usb-recovery-drive#download
McAfee documents that you need this (ridiculous) code to uninstall this program. Their retention/marketing tactics seem to have reached a new level of pain. To be honest, I would not trust any method OTHER than reimaging to get this off your Surface. And you will be safe with the built in Windows Defender.