[starrlordxt]

We need some more info to get a clear picture. But I am going to assume the following: your baby monitor takes a 6 Volt DC input at around 0.4 to 1 Amps (like usual Vtech models). which means the power it consumes is from 3 Watts to 6 Watts.

I would definitely not plug in the 7 Volt adapter as if the current is too high it might damage the circuit.

Whether the 5 volt source can be used would depend on the current. If its a standard USB 5 Volt output most modern day ones are 2 Amps, which would mean the power output is 10 Watts, which may be too much for the circuit. If its 5 Volt, 1 Amp output then it might be okay to connect and test out without damage to the circuit.

What I would recommend is a DC to DC regulator or converter. Something like the following from amazon that would take an input of the 5 Volts and give you 6 Volts out. Make sure to test the output voltage and current with a multimeter before plugging into the monitor.

DC to DC buck converter from amazon: https://a.co/d/9jiA7Ls