I have a five ton R 22 hp commercial system. Can I change the evaporator expansion valve and convet it to a r 410 system?

Probably not. It is more than an expansion valve. In the case of HVAC systems, conversion requires replacing the R-22 compressor, evaporator and condenser with units designed to run with R-410A. Why not keep R-22 it is still available although no longer produced.