You cant do it in a SINGLE prompt but you can do it in a second request
You cant do it in a SINGLE prompt normally because WEBP is the most efficient for DALL-E to return but you can do it in a second request
(Note: ImJPG() is a Function I have saved to Memory which asked to create image based on EXACT phrase and save as JPG - it returns WEBP)
The link below it is PNG as required
It’s a little annoying but may be handy to create a ‘Function’ like:
“Create a function cPNG() and add it to Memory which converts the last image into a PNG and returns a download link”
and then the same again for other formats as required