The 8 digit pin on a HP printer router label is typically located on the bottom or back of the router, near the serial number and other identifying information. The label may also indicate the default username and password for accessing the router settings. If the label has been removed or damaged, the pin may be retrievable through the printer's software or by contacting HP support for assistance. It's important to keep this information secure, as it can be used to access and potentially compromise your network.