Get a radiation meter and measure it.
That's the only way to be sure if you're going to be paranoid about everything, but if you're going to do that, why wouldn't you have already put the AC adapter as far away as the cord allows, or even build an extension cord to further that distance?
The amount of radiation emitted depends on the design of the circuit inside and the shielding of the enclosure. A fixed value can't be assumed for a random unspecified make and model adapter, nor even a specific make and model adapter unless you happen to have a database where someone has made it their mission to test them all, using a team of people sufficient to keep up with the rate of new products produced.
You stated the "safe" distance for a microwave is 2 meters, but that has not been established as fact. The fact is that no matter what you deem a safe level to be (which is also subject to debate), it must be a measured quantity to calculate distance if you do not measure at different distances, and still extrapolate for any distance you don't measure.
If you seek non-factual information then we can make up any (plausible) number we like and just say further away is better.
You have probably been reading misinformation but you are free to limit yourself how ever much you can manage to, but it all comes back to doing your own measurements in your specific environment.