LM317 Adjustable Regulator in a constant current configuration. The current value is set by the resistor value: Iout=1.25/R1. Mounting holes are tied to GND. The TO-220 package maybe soldered directly to the exposed pad to provide thermal relief for the regulator. The input voltage is dependent on the number of LED’s being driven and the forward voltage. Using the LM317 adjustable regulator allows most of the power to be dissipated from the regulator so you may not require a power resistor, but fixed output regulators can also be used but will likely require a high wattage resistor. Just do your power calculations. Altium Designer files are available on Github.