Controlling multiple sets of LEDs from one Arduino (Dice Mechanism)

Hello! I'm a complete beginner to systems like this in general. I'm a design student and we have a block course where we need to design and develop a system that uses 40 white LEDs and a microcontroller (arduino). I'm completely lost and this is due in a few days, we only have a few hours per day to use the lab and the professor doesn't have time to help all of us so I hope I could get some guidance here.

I'm working on a dice mechanism that uses 6 4"x4" PCBs with a number of LEDs soldered on each panel (with a maximum of 12 LEDs on the panel for he number '6') Each panel will have one LDR each. When an LDR detects complete darkness, it will power the LEDs on the opposite side to glow. The expected behavior in use is that you roll the dice and the top face will glow.

Each LED panel will be connected with 6 loose wires to the Arduino we will attach inside the dice.

My questions are:
1) Will it be possible to connect and control the 12 LEDs of one side of the dice to one pin of the Arduino?
2) Will we need a power source attached to the Arduino for this or something?
3) How do we attach resistors to this circuit? Resistors are another headache for us.
4) I have no idea what I'm doing I'm just going by trial and error and barely get it so any other tips appreciated :,)