My boss is giving me work outside my job description and said if we don’t pass inspection, he will throw me under the bus.

I work in retail as a supervisor. We have an upcoming inspection and I was told fully recover the entire store. If it was not done 100% that he would put the blame on me. The task I believe is impossible to be done as usually it is split between two or more people. Last time, he threatened to fire me. This time I’m worried that he will fire me, what should I do.