The first place to look is the website of the manufacturer (often associated with brands like Golden Media, Galep, or generic OEM branding). Search specifically for "ES-9910UB support" or "Downloads." to avoid malware.
These printers rely on to translate complex graphical and text data from your computer (Windows, Mac, or Linux) into commands the printer understands. Without the correct driver, your operating system will see an "Unknown USB Device" or fail to communicate with the printer entirely. es-9910ub driver download