The most needed thing will be intelligence. A strong knowledge of electrical engineering, mechanical engineering, and manufacturing. All that AI and robotics wont work if a strong EM pulse hits the earth like from a sun spot. And we will need the ability to rebuild all the electrical machines, from the generating of electricity to the refrigerators and auto mobiles. Because when a strong EM pulse hits any thing that has a electrical charge in it or once had a charge becomes inert useless. And the only way to protect from this is a very strong faraday cage.