Considering starting over in corrections??

As a brand new LPN, the first full time gig I was able to land was a prison, private owned federal. I was being open-minded about the idea but ended up being there all of about three months. Long story, technically I was fired for 'insubordination'. I was hired for night shift but agree to work days as a favor to the director, as they had someone quit and were already understaffed. When one of the night nurses decided to leave I was told that I would switch to nights, which I had never worked, without training one day after working days, when I had a family obligation. The director, who was from what I hear was a brand new RN and had been on vacation about half of the time I was there. I said that given I had a one hour drive and no notice. There was no way I could do that and did not think it was fair; also I was varily 20 y/o so perhaps I was not as professional as I should have been.

I worked elsewhere (ltc) for two and a half years and just finished my RN. Now I have an interview at a county jail, with medical service outsourced to provate company. I had been doing prn home health, though rarely worked, while working in the prison so I have always ommitted them from my resume as I was only there a few months. How much, or should I mention this past bad experience?? I assume that the security clearance will ask me for every place I ever worked and I will have to put it there, correct?? although it is likely HR not nursing that does that. I am just nervous, don't want to bad mouth my ex-employers or lie. Any suggestions on how to deal with this??

The job itself at the prison was not bad and I am looking to broaden my experience base beyond ltc, with my field of interest being public health.