You’ve not simply done something for the last couple of years: you’ve made a contribution, made something different, made something that changes what came before. Made something that matters. You don’t need a model answer or script to hand to describe what you’ve done for your examiners, but it will help you in the viva to have reflected on how your work makes a difference.
So, quite simply, what’s your thesis contribution?
Before your viva make notes, reflect on your contribution and tell others about it. Then you’ll be more confident discussing what you’ve done with your examiners when you have to defend your thesis.