How to create and what are the requirements to qimplement shopping cart application using ASP.NET Web API as backend and Vue.js(JS,CSS,HTML) as frontend using SQLite database?

I need to know should we need to use postman or swagger to validate Api (PUT, GET, POST, DELETE etc.) or can we implement it by ASP.NET Web API using Microsoft visual studio?

PostMan is a client for testing HTTP calls. Swagger is used for testing and API documentation. Code generators can use swagger to create client code for calling Web API.

ASP.NET Web API is a REST API that either PostMan calls or Swagger documents. There is no problem using PostMan and Swagger.

https://video2.skills-academy.com/en-us/aspnet/core/tutorials/first-web-api?view=aspnetcore-7.0&tabs=visual-studio

if we use Microsoft visual studio for the web Api and VS code for the frontend(vue.js)

Visual Studio and VS Code are development toolchains. I'm not sure why you would use both.

how can we interlink both and perform operation in browser as web application?? can you give idea to implement this with requirements?

I'm not sure how to answer this question. Maybe going through a few tutorials will help you figure out what to do. Start by creating a Web API project to learn how Swagger and PostMan works. Then add a Vue application to make http calls to Web API.

Sqlite configuration is covered in the official documentation.

https://video2.skills-academy.com/en-us/dotnet/standard/data/sqlite/?tabs=netcore-cli