How to extract minimum supply voltage from the datasheets
is 15V OK?


No, the graphs indicate that a supply as low as +/- 8 V (aka a spread of 16 volts) is the minimum just as it says on page 1 of the data sheet.


  For LMF347 it is written that the recommended conditions are min
  supply of 3.5


No, it says the minimum supply is +/- 3.5 volts - that's a total supply spread of 7 volts.


  So I guess 5 volts should be OK?


+/- 5 volts would be fine but not a single supply of 5 volts.


  Is it better to use NE5532 in which the supply is specified for a
  "wide range of 3V to 20V"?


No, the supply is specified as +/- 3 volts minimum i.e. a supply spread of 6 volts. Whether this device is better (or more suitable) depends entirely on what your circuit is intended to achieve performance wise.