if you start your project with this command
ionic start projectname
Go to this projectname folder in this folder you will find the package.json,node module, and the src folder.
so you just have to replace the existing package.json file to this file and then open the terminal
and go to the projectname folder through this command cd projectname.
Then serve this command npm install then it install all the dependencies for your ionic app.then serve the ionic serve.