Powering mutiple Infrared LEDs through a single Arduino Uno pin?
Typical Collector Follower setup.



simulate this circuit &ndash; Schematic created using CircuitLab
Size the R1-R3 for your leds and current, choose a transistor that can handle that current. A common 2N3904 or 2n2222 type transistor would do for a few leds no problem.
Edit:
The IRF520 N Channel Power Mosfet is overkill for this but as the saying goes, there's no kill like overkill (Yes).
Based on the LED specs you provided, you can skip multiple resistors per 3 leds. (Sized for 40 mA instead of 50mA). Add more in parallel as the other circuit.



simulate this circuit