Using Android Studio 3.0 / SDK Manager

In trying to set up BILLING, tutorials show installing it through Extras in SDK Manager.

I don't have an Extras folder in SDK manager and can't find any reason why, how to get it, what's wrong, or what to do.

Help. please?

UPDATE: Here's what my SDK Manager looks like:

[![enter image description here](https://i.stack.imgur.com/cq2y1.png)](https://i.stack.imgur.com/cq2y1.png)

UPDATE: Here's my SDK Manager Updates Tab

[![enter image description here](https://i.stack.imgur.com/o2dJy.jpg)](https://i.stack.imgur.com/o2dJy.jpg)