No need for volt meters, etc.
Set the Camcorder’s audio input(s) to LINE-level.
Send tone out of the FP33 mixer at “0” VU.
Set the adjustable (manual) audio level on the camcorder to about -10 or -12 (or -18) dB.
Make sure that your input TO THE MIXER is set correctly for the type of source being sent.
As in, if you have a LINE level from the house console, make sure you are feeding a line input setting on the FP33.
Do a test before the shoot and listen with your headphones coming first directly from the FP33 MIXER… then, listen coming from the CAMERA’S audio output.
Everything should sound “clean.”