Can't open old HP scanjet driver

Thanks to guidance on this site, I was able to install the driver and update for the HP scanjet 5530 (machine is more than 10 years old and no longer supported by HP). Had to change firewall preferences to allow them to install on my macbook air.

Now, I can't open the application. This is the notice:

You can’t open the application “Scanner Preferences.app” because PowerPC applications are no longer supported.

Also, the computer doesn't acknowledge the connection to the machine under Devices in the Finder. The driver app is listed there, though.

Any suggestions, please?

Thank you!