Vue cdn, component from file?

Question

Vue.js

When connecting Vue via NPM and working with components, everything is clear. The component can be connected from a file, everything works.
But when connecting Vue via CDN, it is not possible to connect the component from the file.
Here is an example code:

import firstComponent from 'firstComponent.js';

new Vue({
    el: '#app',
    components: {
        firstComponent
    },
});

Gives the error "SyntaxError: import declarations may only appear at top level of a module".
I tried to add the type="module" attribute in the script tag of the included js file, but then nothing works at all.
Tell me what's the problem?