printer supplies for HP Envy Pro 6455

Contact HP support request. This is for Browser help not a online order site.

need to order ink for my printer HP ENVYPRO 6455

Not sure why you are asking here when Mozilla nor the Firefox web browser has anything to do with HP printers.

A search for HP ENVYPRO 6455 ink in a search engine search like Google.com, duckduckgo.com or such depending on where you live will likely give you plenty of places you can buy this ink cartridge in retail stores and places you can order online.