I have an iPad 9th generation. How can I print using a usb cable to my printer

iOS/iPadOS doesn’t natively support direct connection to a USB Printer. Instead, these devices use a network connection to supported printers typically over WiFi - or if explicitly supported by the printer, a wired ethernet connection.

See:

• Use AirPrint to print from your iPhone, iPad, or iPod touch - Apple Support
• Connect an AirPrint printer to a Wi-Fi network - Apple Support

Apple AirPrint is a driverless connection protocol. A high proportion of modern printers intended for Home, SoHo and Business environments now support AirPrint. Check your printer model against this list:

About AirPrint - Apple Support

If your printer is not compatible with AirPrint, there are alternatives…

Some printer manufacturers have a suitable companion App that provides Print capabilities for mobile devices, often using a web-based print service. Others can print directly if the App supports other network printing protocols. By example, many HP Printers use the HP Smart App - available in the App Store:

https://apps.apple.com/gb/app/hp-smart/id469284907

You might also consider connecting a non-AirPrint printer to a PC or Mac computer - and install a “helper application” that allows the computer to emulate AirPrint capabilities; one such option is Readdle Printer Pro, for which suitable software for PC is available. A link to the PC software is included from this page:

https://readdle.com/printerpro

A further alternative is to consider installing a dedicated Print Server Appliance on your network - and connect your printer to this. One example is the Lantronix xPrintServer.

The remaining solution is to simply replace your printer with one that is AirPrint capable.

Not a feature of iPadOS. iPads print to printers that have AirPrint capability.

This link will provide more information:

Use AirPrint to print from your iPhone or iPad - Apple Support

Some printers have their own apps which will allow you to

print if connected to network or Mac/PC.

If you post the manufacturer and model identifier of your

printer, someone may offer a better solution.

If there is a manufacturer-provided companion printing App for the printer, it may support printing via Bluetooth. Otherwise, all the information outlined in my initial reply, concerning AirPrint, still applies.