If you have a standard USB Type-A cable, the most useful adapter to make the connection - and simultaneously charge the iPad using your standard Power Adapter - would be an Apple USB-C Digital AV Multiport Adapter:
https://store.apple.com/uk/xc/product/MUF82ZM/A
You might alternatively consider a compatible third-party USB-C hub - that incorporates a number of alternative ports. 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 various USB 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.