It is not possible to connect one of our interfaces to an iPad with a USB adapter. The 30 pin and Lightning ports are heavily controlled by Apple ( https://en.wikipedia.org/wiki/MFi_Program ), and our older products won’t pass the certifications for various reasons, mostly related to Apple’s control over the connector.

The USB adapters that do work will only talk to items such as USB and SD storage, meant for transferring photos. These same adapters do not work to connect to printers, keyboards, or other USB devices. Apple is unlikely to add a standard USB port to iOS devices, or make it possible for older USB devices to connect.

We do have several products that allow you to use your existing sensors with iPads.
https://www.vernier.com/platforms/mobile/ipad/

Related:
How can I update to new Vernier equipment and still make use of my old Vernier equipment?