Is prisma an alternative to apollo client?

Apollo client is to help you query any graphql endpoint from the frontend and has a lot of robust frontend caching features. Prisma is like a database endpoint for your backend. It provides an ORM layer on top of your database. You're not supposed to directly hit prisma from your frontend using the apollo client. You need to have another server on top of your prisma server. That other server is your GraphQL endpoint that gets consumed by your apollo client on the frontend.

So, here is what I understood, prisma is an ORM setting up the database model and sends queries. I need an apollo server to receive graph queries from the apollo client.

Yes that is correct, you can use Yoga or Apollo or other frameworks for the GraphQL server. You can use something like Heroku to get it set up quickly.