Module not found: Error: Can’t resolve ‘core-js/es6’

The imports have changed for core-js version 3.0.1 – for example

import 'core-js/es6/array';
and
import 'core-js/es7/array';

can now be provided simply by the following

import 'core-js/es/array';

if you would prefer not to bring in the whole of core-js