Please open cmd or terminal and navigate to your ionic project folder where your src folder is and try running this command :
npm install [email protected]
Try the above method first but if issue does not resolves then take backup of all ionic setup then
rename the node_modules folder in your ionic project (where src folder is) to node_modules_BACKUP and also rename the package.json file to package_BACKUP.json .
then download the package.json file from here : https://bit.ly/2I2F732
Then place it in your ionic project .
Then in terminal of cmd run :