Apple HDMI adapter (with Lightning connection and USB-C

The iPad Lightning port presents both proprietary Lightning and USB connection via a suitable cable. By contrast, Lightning accessories connect directly to the iPad Lightning interface - effectively bypassing USB connectivity.

Consider that with USB-C, you can now add multiple additional interfaces with a single adapter or USB Hub - where this was not previously possible with Lightning.

There are many USB Hubs that have a USB-C connection for iPad plus a USB-C PD (Power Delivery) pass-through power connector to which you can connect your USB-C Power Adapter - along with the hub itself incorporating a combination of additional USB-C ports, USB 2.0/3.1 Type-A ports, Ethernet LAN, HDMI, VGA, SD and microSD card-readers.

Perhaps consider Kingston, Anker, Hyperdrive and Satechi - although there are many others from which to choose. A Google Search for USB-C Hubs compatible with iPad will find a number of articles and recommendations. 

Speaking of personal experience, the Kingston Nucleum has proven itself to be particularly flexible for connection of high power USB storage devices - featuring twin USB3.1 Type-A, downstream USB-C and SD/microSD card slots, HDMI, plus a power pass-through USB-C port that can accept +45W from a suitable USB power source.

If looking for an HDMI Adapter, be aware that few USB-C HDMI adapters/hubs support HDCP 2.0 - absence of which will inhibit the ability to output copy-protected HD media content from iPad to a connected monitor/TV over an HDMI connection.

The Apple USB-C Digital AV Multiport Adapter does support HDCP 2.0, but lacks the flexibility of many USB-C hubs:

https://store.apple.com/uk/xc/product/MUF82ZM/A

Note also that most iPad models that feature USB-C also support DisplayPort Alternate Mode over USB-C. This protocol allows direct connection, with an appropriate Thunderbolt cable, to a monitor that supports DisplayPort - removing the need for HDMI.

USB-C and Apple’s proprietary Lightning connectors are entirely different interfaces - both electrically and physically - and are not inter-workable. As such, you cannot connect Lightning accessories to USB-C.

Whilst interconnection of USB-C and Lightning isn’t possible, you do benefit from USB-C’s significantly improved bandwidth/throughput and connection flexibility. To fully benefit from USB-C, you’ll need to use USB-C hardware and/or purchase suitable adapters.

If you have an iPhone, all of your existing Lightning accessories remain fully usable.

Whilst very good, not all Apple staff are knowledgeable of all aspects of all Apple products - and for this reason alone, it is always worthwhile to ask questions in a technical forum such as this.

Whilst ASC contributors are all end-users, like yourself, many regular contributors possess in-depth knowledge that can only be gleaned from regular or daily use of the very products for which you seek help. Of course, you will need to establish for yourself confidence in the information that you choose to trust.