Antenna transducer factor translation issue

Dear All:

I want to show the dBm unit in the specturm when it connect with directional antenna.
But the AF unit is dBuV/m . The spectrum can only show dBuV unit.

I try to transfer the AF unit to dBi.
Ex: Antenna at 500MHz, the AF=18.707 dBuV/m.

I will use the below formula to transfer the unit.
AF (dB) = 20 * log ( 9.73 / [lambda * sqrt(Go ) ] )

But I don't sure that this transfer is correct or incorrect.
Do you have any suggestion about this issue?

The unit doesn't make sense. Generally, the antenna factor links an antenna output voltage/power (in dBμV respectively dBm) to a field strength (in dBμV/m) at a particular frequency. Thus it can't have the above unit. Alternatively, an antenna gain related to an omnidirectnal antenna may be given.