My answer in post #2 applies to conversion of GE 90-30 hardware to any of the Siemens S7 PLCs. It also applies to conversion of the ladder logic in the 90-30 to a program that will run on that Siemens S7 platform.
The question about a utility to convert from brand X to brand Y has been asked dozens of times. Ask yourself this. What would be the incentive for anyone to create such a utility? Do you think that any PLC vendor could generate enough revenue from it to cover the developments costs? The PLC vendors don't seem to think so since they haven't developed any.
The fundamental difficulty in creating a conversion utility is this. Without some understanding of the process controlled by the PLC, translating individual rungs of logic is somewhat akin to translating a document by looking up individual words in a dictionary.