Charger

Some PowerBank batteries have a USB Type-A connector - and some have a USB-C connector - and some have both. Many are supplied with one or more cables with which to make connection to your iPad/iPhone/other device. You simply need to ensure that you have the appropriate cable for the interconnect.

Your iPad Pro (inferred from the tags appended to your original post) suggests that you have an iPad Pro. Depending upon model, it will either have a Lightning connector (and was supplied with a USB Type-A to Lightning cable) or a USB-C connector (and was supplied with a USB-C to USB-C cable). The cable with which the iPad was supplied does not limit you to the corresponding connection; you can purchase the cable that you need.

Using Mophie as an example, their PowerBank products are usually supplied with one or more cables with different connectors.

https://www.zagg.com/en_eu/universal-batteries

Your main point of consideration might be better focussed upon the overall power capacity of the battery pack. PowerBank devices intended for an iPhone are often inadequate for an iPad that has much greater power needs and internal battery.

I hope this insight and clarification proves to be helpful.

Isn’t the Power Adapter, as supplied with your iPad, not portable enough for you? They’re pretty small!

Are you perhaps, instead, looking for a PowerBank (battery) with which to charge your iPad whilst travelling and are away from mains power? If so, there are many to choose from - from a number of reputable manufacturers such as Mophie (these also being retailed directly by Apple).