The Pre-amp just says 12v. Not any specific amps. So there's not enough info to work it out. That amp already comes with a 110v to 12v adapter. The pre-amp might say what wattage or amps on it.
buy the amp first and look on the power adapter for the rated amps then get a 240v one that has the same rated amps. I sent a message to the seller asking the amps of the preamp, but my guess is that that adapter will have enough power.