I 'think' the US NES requires 9v AC 1.3A, which is the same as the PAL NES and PAL SNES power requirement, but im not entirely sure as I dont own a US NES. I do know that the JPN Famicom is different to both of them.
If nobody else knows/replies then your best bet is just to check the label on the bottom of the console which will tell you all the power requirements, and the adaptors usually have the power outputs marked on them aswell. This way you can match them and make sure they are correct
Just remember to check the Voltage, if its AC or DC, and if its DC what the polarity of the plug is