To update dependencies in package.json files, you can use npm, the package manager for Node.js:

1. In the terminal, navigate to the root directory of your project and run npm install or npm i to install all the dependencies in your package.json
2. To update a specific dependency, run npm update package-name (package-name is the name of the dependency you want to update, so adjust that text within this command).
3. To update all dependencies, run npm update

To update npm itself, run the following:

npm install -g npm@latest