jar to create a custom plug-in

Hi,

I am trying to do a Custom Plug-in, and i am following the documentation guide where can i find the following jar:

Add the following Appian JAR as an external dependency and click OK.

• <APPIAN_HOME>/_admin/sdk/appian-plug-in-sdk.jar

I know it's giving that directory but i don't have the folder "sdk" on my appian application.

So any idea where can i find it?

Thanks