My home-pc has been hacked ... Office and more

I purchase a full Office Home & Business 2016 a few years ago, and installed it onto my pc at home. I have been hacked and have lost many of my applications on my pc, including Facebook, Instagram, Skype, and many others ...  when any of MS programs launched, a message "ACTION NEEDED Your license isn't genuine, and you may be a victim of software counterfeiting. Avoid interruption and keep your files safe with genuine Office today. Get genuine Office".

I still have the original package packaging with the Product key. How do I solve this conundrum? Please assist. Gary