Power 9 IR LEDs 850 nm with a forward voltage of 1.7 V and forward current of 100mA
The power needed will be 1.7 V * 0.1 A = 0.17 W

GPIO pins cannot be used directly, because for most MCU the absolute max rating is between 10 and 40 mA.

For the power supply you have lots of options. You can e.g. use a 5 V adapter. 

For the 4 times 2 LEDs in series you need the following resistors:

V = I * R &lt;=&gt; (5 - 2 * 1.7) = 0.1 * R &lt;=&gt; R = 1.6 / 0.1 = 16 ohm


And for the power through the resistor:

P = I^2 * R = 0.1^2 * 16 = 0.16 -&gt; So a 1/4 W resistor will do


For the leftover LED:

V = I * R &lt;=&gt; (5 - 1.7) = 0.1 * R &lt;=&gt; R = 3.3 / 0.1 = 33 ohm

P = I^2 * R = 0.1^2 * 33 = 0.33 -&gt; So a 1/2 W resistor will do (or 2 66 ohm resistors in parallel)


The power rating for the adapter will be 0.17 W (and probably you also will power the Raspberry from it).