multiport av adapter

Yes. The USB-C Digital AV Multiport Adapter supports connection to a TV/Monitor via HDMI - in addition to connection of USB Accessories via the USB3 Type-A port. The Multiport adapter also features a pass-through USB-C port for connection of your Power Adapter.

Be aware that HDD devices require significant power to function correctly. If the HDD does not have its own source of power, you may need to connect the HDD via a powered USB hub.

There are alternatives to the Apple’s Multiport Adapter; whether or not they are “better” will be determined by your needs.

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:

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.

You are very welcome.

Your USB-C drive may be usable via a direct connection to your iPad - but if other devices are to be simultaneously connected, you’ll need to use a USB-C hub with a pass-through USB PD (Power Delivery) port with which to provide connection to a Power Adapter.

Remember that every device requires power to run - including the hub itself. For power budget, allow up to 20W for the iPad plus sufficient additional power for the hub and other connected accessories such as your HDD. I suggest a USB-C Power Adapter of +30W - although the upper limit will be determined by the power input of the hub, beyond which additional power from a Power Adapter is not available to connected devices.