An iPad with a USB-C port can connect directly to supported USB storage devices. You have no need for Lightning adapters - and in fact, attempted use of Lightning in the connection chain will very likely be unsuccessful.
If your USB Storage features the older (larger) USB Type-A connector, you will simply need an appropriate USB Adapter to connect the device to the USB-C port of your iPad:
- USB-C Digital AV Multiport Adapter (recommended):
https://store.apple.com/xc/product/MUF82ZM/A
https://store.apple.com/xc/product/MJ1M2ZM/A
You might instead consider using a suitable USB-C hub - as these often include multiple connections for USB-C, USB Type-A, Ethernet LAN, HDMI, SD Card and other device connections. 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.