The article provides a comprehensive overview of migrating a project from Strapi version 3 to version 4, using the Food Advisor app as a case study. It outlines the general steps involved in the code migration process, emphasizing the need for manual updates due to significant changes in the Strapi framework, such as the decoupling of controllers from GraphQL resolvers and the introduction of new features like the "populate" function. The migration process includes updating backend code, configurations, dependencies, and manually refactoring custom routes, controllers, and services to align with Strapi v4's architecture, which now utilizes factory functions for generating core API components. The guide also delves into creating custom controllers and GraphQL resolvers in Strapi v4, offering practical examples and directing readers to additional resources and documentation for resolving potential issues. The article encourages engagement with the Strapi community and documentation to facilitate learning and troubleshooting, underscoring the necessity of adapting to new structures and conventions introduced in Strapi v4 for a successful migration.