Solid core mig wire with CO2/Argon mix gas is what I use. Not a fan of flux core on the small home machines.
Forgot to add, with the amount of holes and craters you have to fill on that plate, you would probably be better served by a Tig. You’d be putting a lot of heat on the toe of that plate with a Mig. But if you do, small tack, let cool, grind/file flush, repeat till you’ve got it.
Bob