I am learning mongodb, and I have already installed packages like mocha, mongoose, and nodemon in the previous project using npm install command, and I am working on a new project, so do I need to install all these packages again, as I have already installed int the previous project?
Assuming you didn't use npm install -g <packages> then yes, you should installed them again if needed. When install with npm install <packages> installed packages get placed in a node-modules folder in your project root directory