You extract the bytes as two IEEE 32 bit floats. There are quite a number of IEEE float32 extractors out there in google land. it's not mc code, 'cause you are extracting it in your environment at the other end of the sigfox link (and I don't know what that is).

I did help someone else with the same problem here in the forums somewhere, if you search carefully you can probably find it, should explain everything.