Apple has discontinued its $29 Lightning to 30-Pin Adapter.
The adapter was first introduced in 2012 when Apple released the Lightning connector with the iPhone 5 and new iPads. At the time many people used this adapter to connect existing 30-Pin devices to Lightning accessories and also to charge existing devices.
Apple has now pulled the device listing from its website. It's been 6 years since this adapter was released and Lightning introduced with Apple's mobile devices so there's no longer any need for this.
If you want one for whatever reason, you may still find the accessory on sites like eBay, but limited numbers of those devices and cables are still in use in 2018.