If you're going to replace all the LEDs of a Dioder, then you might as well replace the whole thing, including its wiring and power supply. If the power supply is anywhere from 9 to 15v (12v is typical for LED strips), then you can use any number of LED strips. However if you don't know what you're doing you'd better read up a little bit on voltage, current and resistance, the absolute basics. As well as how to calculate wattage (current x voltage). What you'll need to be careful of is that you don't overload the power supply with the new LEDs. You'll need to know how much current the new LEDs are pulling (at the voltage of the supply) as well as how much current the power supply can deliver. Allow 15-25% head room (that means the power supply should be able to supply 15-25% more than your LEDs need).