What type of cable do I have to use for use my iPad with a normal priner ?

There is no cable that I know of that will allow you to print to any printer from your iPad. The iPad prints using AirPrint specifications via Wi-Fi. The iPad will print to any AirPrint enabled printer. The pad will also print to other printers using apps from the printer manufacturer or from third party developers. Search the app store for these.

The iPad can also print to networked printers using a hardware device like the XprintServer. Google this if you are interested.

None of these methods, however, use a cable attached to the iPad.

iOS AirPrint Printers
http://support.apple.com/kb/HT4356

How to Print from Your iPad: Summary of Printer and Printing Options

http://ipadacademy.com/2012/03/how-to-print-from-your-ipad-summary-of-printer-an d-printing-options

Print from iPad / iPhone without AirPrint

http://ipadhelp.com/ipad-help/print-from-ipad-iphone-without-airprint/

How to Enable AirPrint on a Mac and Use Any Printer

http://ipadhelp.com/ipad-help/how-to-use-airprint-with-any-printer/

 Cheers, Tom 😉

I use FingerPrint to print to my non-AirPrint printers. See www.collobos.com.

If you're utilizing an HP printer manufactured within recent years it should have e-print capabilities as well which is another free option, downloadable through the apple app catalogue.