Migrate MERN Web App Backend from Postman to Node

I need a skilled developer to migrate my existing, subscription-based MERN web app's backend from Postman to Node.js.

Key Responsibilities:
- Migrate the backend to Node.js
- Ensure the backend supports:
- User authentication and authorization
- Payment processing
- Data storage and retrieval

Please note that while there is existing Node.js code available, the successful freelancer will need to:
- Thoroughly understand the existing code
- Seamlessly integrate the migration without the need for new features or improvements

Ideal Skills:
- Proficiency in Node.js and MERN stack
- Experience with backend development and migration
- Familiarity with user authentication, Stripe payment processing and data management
- Everything is built, I only need it being migrated from Postman to Node.js

I am looking for a professional who can ensure a smooth transition, so my customers can continue to enjoy uninterrupted service.