No-one can provide you with a meaningful, useful checklist for your system. Because it's an INTERNAL audit, it means an audit of your processes and, as a result, since none of us have seen your processes, no-one can provide a checklist! Sure, we could give you some basics, a bit like telling you to write down some basic things to get when you visit the grocery store, but, even that's not going to be much good, without knowing what you actually need!
Sadly - for you - it will take effort to plan your audit and create your own checklists. But, as you may know: "No pain, no gain!"