e.g i have used Apollo server along with Mongoose to fetch data in the resolvers, where do you think Primsa can come in to make things easier

With prisma you a get a type safe and easy way to access your database. We also provide a subscriptions API that will be a pain implementing with mongoose and a websocket transport. Prisma is also very efficient as it batches stuff and solved the n + 1 problems. We also provide a roboust relay styled pagination API