Where is google_ad_slot ID?

I installed the plugin and it asks me the google_ad_client and I know it, but it asks me also the google_ad_slot ID
and I don’t know what is it and where I find it.

The lines I need adding inside the file:
/mysite/wordpress/wp-content/plugins/jetpack/modules/minileven/theme/pub/minileven/content.php

are:

<script async src="//pagead2.googlesyndication.com/pagead/js/adsbygoogle.js"></script>
<script>
  (adsbygoogle = window.adsbygoogle || []).push({
    google_ad_client: "google_ad_client",
    enable_page_level_ads: true
  });
</script>

So I don’t know how use this plugin.

https://wordpress.org/plugins/jetpack-mobile-theme-ads/