There are several variations of the POS-9210-L firmware. The most common driver for this hardware is the or general POS-58 series driver, as the internal mechanisms are often shared across these models.
Most POS-9210-L units are manufactured under generic Chinese brands (e.g., Xprinter, Hprt, or PosBoss). Check the sticker on the bottom of your printer. Thermal Printer Pos-9210-l Driver - Download