You saved an image from a website and got a WebP, and now something refuses to open it. Converting to JPG solves it in a few seconds.
WebP produces smaller files than JPG at the same visual quality, which is why sites serve it. That is good for the site and occasionally annoying for you, because plenty of older desktop software, printers and forms still do not accept it.
Converting to JPG costs you a little quality, because both formats are lossy and you are re-encoding an image that was already compressed once. At 85 per cent nobody will see the difference in a photograph, though flat graphics and screenshots fare less well.
If your WebP has a transparent background, convert to PNG rather than JPG. JPG has no transparency at all and will fill those areas with solid white, which is rarely what anyone wants.
A small amount, since it is a re-encode. At sensible quality settings this is invisible in photographs.
Use PNG instead. JPG cannot store transparency and will turn it white.
Yes, add them all and convert in one pass.