Portable Generator Feeder

[tlona1]

I am installing a 125KW portable generator. It is supplying a 250A ATS which is then feeding a 208V 3-phase 250A data center panel. Both the generator and ATS are outside and about 20ft apart. Can I use a cord (portable power cable type 'PPE' )to feed the ATS from the generator. Also, does my cord need a ground. The cables will be run along the surface of the ground and protected by rubber covers. Thank-you