To identify image files, use the following snippet:

import sys
from PIL import Image 

for infile in sys.argv[1:]:
   try:
      with Image.open(infile) as im:
          print (infile, im.format, f"{im.size}x{im.mode}")
   except OSError:
          pass

To convert file sto JPEG, use the following snippet:

import os, sys
from PIL import Image

for infile in sys.argv[1:]:
    f, e = os.path.splitext(infile)
    outfile = f + ".jpg"
    if infile != outfile:
        try:
            with Image.open(infile) as im:
                im.save(outfile)
        except OSError:
            print("cannot convert", infile)