I'd like to know if there's an MKS unit system in which electric and magnetic fields have the same measurement unit. I couldn't find anything like that on the internet. Does that system exist? Do people use it? What is it called?
It is called natural units. Very simply, all dimensional conversions are set equal to 1: $$c=\hbar=\epsilon_0=\mu_0=1 , $$ and so forth. It is commonly used in particle physics.