Take that range cord back and get the correct cord for the job
50A generator inlet boxes, as well as many generators with 50A outputs, do not use anything resembling the NEMA 14-50 that is certainly on the end of your range cord. Instead, they use locking type connectors; unfortunately, there is no such thing as a NEMA L14-50, so California had to step in and set their own standard for this, the CS6365C/CS6375 family. Furthermore, the type SRD cordage that is used for range cords is not rated for wet locations or hard/extra-hard usage, making it utterly unsuitable for use outdoors, even if your generator uses a NEMA 14-50R for its 50A receptacle.
As a result, you're better off taking all your stuff back and getting the proper generator cord for your generator. This will have a CS6364C cord-connector on it to mate with what is almost certainly a CS6375 inlet on the generator inlet box, and be made from extra-hard usage, wet-rated cordage such as type SOOW, with a 6/4 wire configuration, and either a NEMA 14-50P or a CS6365C plug on the other end, depending on what your generator uses.