You generally find them in caches on the map when playing (highlighted beacons you can see from a fair distance). The super credits are automatically given to everyone when one person picks it up.

Technically, there's a way to farm these indefinitely by essentially replaying the same map. But you can't unlock the guns/capes/gear in each warbond without medals, which you can only get by doing missions.

Personally, I like the gameloop and how microtransactions are done enough that I don't bother with the "farm" since credits are so easy to gain overtime. The real grind is the medals and samples which you need a team to gather efficiently.

You play the game? You usually find credits on most maps. Not huge amounts, but it adds up. Also, every warbond comes with unlocks that give you some super credits for medals.

with medals? I don't think that's a thing.

super credits can be purchased using real money, or you can just find them in-game. it's always a good idea to sweep the map completely before extract.