big led project

Hello CrossRoads I'm back, been doing a lot of reading, got the arduino UNO and been looking for the resistors but apparently these are hard to find.... Anyways Got a few questions I can't find any info on how the MOSFET will convert the voltage from 5 to 12 and 24v??? Will i need a mosfet driver or will the arduino do it?? Which mosfet will I use for the 24v led strips and which one will I use for the 12v strip??? Also u gave an example of 30mA going out of the arduino, I believe to find the amperage of the light Is the wattage divided by the voltage right?? In that example why 30mA??, where does that figure comes from? Is that for the MOSFET or the lights?? Maybe that depends on the type of MOSFET to be used if it is for this??
I'm sorry for the ignorance but it hasrelly been long time since I did something like this.
And trully never worked with MOSFETS And thank you for the help