I don’t see index and follow in the meta robots tag

You’ve written a post and configured its Advanced settings in the WordPress SEO (Premium) metabox, like this:

Metabox Advanced

However, when you look at the resulting source code for your post, you do not see the meta robots tag.

<meta name="robots" content="index,follow"/>

The sole reason; index,follow is the default meta robots setting, thus there’s no need to explicitly add it.