misa,
no, that is very very wrong.
dB cannot be converted in dBm ! those are not counting the same thing.
dBm is an absolute power. It can be converted in Watts.
2W = 33dBm
dB is a difference of dBm, and it has no physical existence other than this. It is a mathematical tool.
For example, from 39dBm to 42dBm, there is a difference of +3 dB.
You cannot convert 3dB to watts. But you can convert dBm into watts.
39dBm = 8W
42dBm = 16W
but 3dB is not equal to 8W !!!
Regards
pix