Brakes really weak

Hey all. Just bought a 74 duster 225 auto. The brakes "work" but they're really weak. You need to put the pedal in the floor to get any stoppage. I checked the pads and they should be replaced and the fluid is really dirty but full. Do you think flushing the system and replacing pads and rotors will fix this? Also how do you get the rotors off because I couldn't figure it out. Thanks

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Author: Mason Moran