dBµV (decibel-microvolts) is a unit of power in decibels when referenced to 1 microvolt per meter. It is generally used for electric field intensity measurement.
dBm (decibel-milliwatts) is a unit used to indicate that a power level is expressed in decibels (dB) with reference to one milliwatt (mW).
dBm is expressed as:
dBm = dBµV – 10log10 (Z) + 90
Z is the system impedance