In most interviews I've had they asked what do I think the job involves, so make sure you know the sort of things that you will be expected to do.
It sounds easier than it is, but try to relax. The worst that can happen is you won't get the job and you will never have to see them again, so don't worry about saying anything stupid.
Think about what you can put into the job, and what you want to get out of it.
Also, emphasise the experience you already have and how that relates to working in a nursing home.
If you can, ask someone to pretend to be the interviewer and have a practice at answering questions.