using an arduino pro mini with a 12v Power Supply and make 2 sets of leds flash

Good day, I'm pretty new to this wonderful world !

I'm having issues finding the documentation for this kind of design.

what i want to do is make 2 sets of parallel leds flash one at a time via pin 9-10 on the arduino pro mini.

and power the leds and the arduino with a 12v power supply, but heres the trick i want to use the power supply directly on the leds so they flash really bright, since if i plug the power in the arduino i understand that it reduces the power to 5v and then the leds are really dim.

is there a way to do this ?
I've seen a couple of options for a led strip using a mofet, but does that apply for my project?

thanks in advance for your help !

LED brightness depends on current thru them, not the supply voltage.
Flashing one after the other is easy:

void setup(){
pinMode (9, OUTPUT);
pinMode (10, OUTPUT);
void loop(){
digitalWrite (9, HIGH);
delay (100);
digitalWrite (9, LOW);
digitalWrite (10, HIGH);
delay (100);
digitalWrite (10, LOW);

Having a transistor to buffer the two IO pins and sink the needed current from a 5V or 12V source is also pretty basic.