Can I supply a voltage at a specific current? I doubt it
If the LED module needs 24V 5A, it likely needs 5A constant current, and the resulting voltage could vary, up to 24V in worst case, and likely quite less in reality. 

If you have only a 30V DC power supply with no CC (Constant Current) limit mode, an "adapter" could be as simple as a resistor. 

You would need to drop 6V (30V - 24V), and to have the 5A current, you would need about 1.2 Ohm resistor. It must be a sizable wirewound resistor capable to dissipate 30 W, a big one. It will be good for a quick experiment, but for real work you would need a dedicated "LED Driver", which is a AC-DC CC-CV power supply with reduced quality.