What is the ECG finding for an atrial fibrillation and atrial flutter?

This. In atrial fibrillation, there are no P waves seen, or the P waves are highly irregular and not directly correlated with the qrs complexes. In atrial flutter constant, regularized activity is seen, generally without a fixed baseline.
Fib/flutter waves. There are small waves from the atrial activity on 12-lead ecg. Normally these are single, well defined P waves during sinus rhythm. For flutter, they are rapid and regular, often with a "sawtooth" pattern. For fib, the atrial activity is very random, irregular, and sometimes hard to see. Atypical flutter can be hard to distinguish from "coarse" af by ecg.