square root of 5 input numbers

[perfringo]

how can I use return here

Use return outside of for-loop. This means that it returns after all elements are appended.

EDIT:

If you are happy returning list of strings (as your code does) then it's OK. If you need perform any calculations later, you should probably convert to float.

import math

def lists(*args):
    return [float(f'{math.sqrt(int(arg)):.2f}') for arg in args]