How do I connect my iPad to an hp printer

Perhaps this applies. “[HP] print[er]” includes many different models.

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

if its a wireless printer that you can print documents with it if it supports it. if its a printer that uses usb-a cable to print (assuming its usb-a) you can use a lightning to usb-a dongle (ipad with home button) or a usb-c to usb-a dongle (ipad without home button)