Hi,
To check the Tx power values, you would need a spectrum analyzer to measure them, while generating traffic for all modems.
May we know why you would like doing it?
The IXM LoRaWAN is calibrated at manufacturing. The values are displayed under "show radio" in standalone mode or "show virtual-lpwa N modem info" in IOS mode.
If you are looking at developing a LoRa forwarder software, I recommend you read
https://community.cisco.com/t5/cisco-lorawan-blogs/about-the-native-semtech-packet-forwarder-v5-1-0-binary-pre/ba-p/3664346
Regards
Patrick