The general rule is to match the V(voltage) and equal or beat the mAh (current rating).
CHECK YOUR LABELS FOR ADAPTER INFORMATION
The adapter output V matches the rated input V of the device.( AC TO AC) OR (AC TO DC)
110VAC/6vAc or 110VAc / 6vDC
The adapter output can be greater or equal to the devices rated mAh or A. But not
less than current rating.
1200mAh is equal to 1.2A(amps)
Side of unit
Plug size/ Polarity
Pick out the correct tip for your device and select the correct polarity.(Most Xmas units are center pin positive outer negative. Also if the unit needs to plug in the bottom, you may need an L-shape tip.