>What should I use to measure and display the MV of load
>cells in 4 or 6 wires load cell concept before I feeding the
>signals to summing box?
A millivolt meter.
The cells are normally rated something like 1 mV/Volt per kg (don't quote me they are all different but look up the specs). They put out zero with no load on them. Make sure you don't mechanically overload or the zero will be permanently offset. Too much excitation Voltage is also not good.
One of the best ways to evaluate a load cells mV/V output would be to review the calibration certificate, or results, as the mV/V is the electrical output of the load cell while under a known load divided by the supply voltage.