First delete all the widgets from the dashboard, then make the below changes into your code and upload it. this will populate your dashboard with widget, add them.
int p;
CAYENNE_OUT_DEFAULT()
{
Cayenne.virtualWrite(0, millis());
Cayenne.virtualWrite(1, bme.readTemperature(), "temp", "c");
P = bme.readPressure() / 100.0F;
Cayenne.virtualWrite(2, P, "bp", "pa");
Cayenne.virtualWrite(3, bme.readHumidity(), "rel_hum", "p");
}
Have a look at this Data types for Cayenne MQTT API