3 Days Notice to Quit, after Tax Sale

[Mike MoRo]

I bought a property from the County Tax Sale. There is lady living in the house without paying rent or anything for the last 3 years, after the previous owner past away. I've been trying to help her move out of the house for the last 30-40 days, but she won't even make an effort. I've decided to give her a 3 days Notice to Quit. What reason should I write in the Notice?

Thank you