Surge protectors

Told you there are a bunch of questions, this 50 amp thing is all new to me.  I believe in a surge guard of some kind.  but if you have a portable guard and the camp ground only has 30 amp service.  Looking though all I find are male plugs that go into the camp ground box, not a female end that attaches to our marinco on the side of the coach.  Other than a 50 to 30 amp adapter on the camp ground side, then a surge guard, then your cord to the coach?  What else?

There are several threads on this forum about electric management systems, either built in or plug in, each with their own advantages. They not only protect from surge, but also under and over voltage (a real and damaging danger) reverse polarity, improper ground, frequency, etc. Here's a link to a popular provider that has both types:

  https://www.progressiveindustries.net/

Yea, actually have a couple, but not quite what I asked.  Every thing seems to be backwards when dealing with a marnico coupling.