This error message indicates that the version of Ionic IIS is not compatible with other CLI plugins (see https://github.com/ionic-team/ionic/issues/12561 ).
Please run the following commands in the project directory (where you have package.json):
npm i -g ionic@latest
npm i --save-dev --save-exact ionic@latest
This will install the latest version of the Ionic CLI (currently 3.7.0) worldwide and locally. After that, the error should no longer appear.