Sorry but microwaves do not make good Faraday cages. Yes they will shield the device but they are heavy, small capacity, lots of wasted space and fairly heavy.
All you need is a metal box with the inside covered by a basic insulator. A metal garbage can with cardboard is sufficient as long as the lid fits tight.
Yes, a metallic screening is very effective against it but the problem electronics is still need cables to work and you can’t fully protect it for that reason. Spark gaps and things like that are of some use at that point and optic cables are somehow immune to magnetic pulse as well.