In order to find the power (P) in Watt of a driver, we have to multiply its voltage (U) in Volt by its intensity (I) in Ampere:

P = U x I
W = V x A

Example :

Let’s take our DCC 15-350CG (code : 1600131).
Output current = 350 mA = 0,35 A
Minimum voltage = 27 V
Maximum voltage = 42 V

So
Minimum power = 27 x 0,35 = 9,5 W
Maximum power = 42 x 0,35 = 14,7 W