Convert WEBP to PNG
WEBP is smaller, but plenty of software still refuses to open it. PNG is the safe, lossless answer.
WEBP is better; PNG is safer
Saving a WEBP image is a strange thing to need. The format is smaller and better supported by browsers than it was five years ago, so if the image is going on a web page, leave it alone.
The conversion is for everything else: pasting into a document, uploading to a system that checks the extension, opening in an older editor, or sending to someone whose software shrugs at it.
PNG is the right target rather than JPG because WEBP can carry transparency and JPG cannot. If the image has a transparent background, JPG would fill it with white; PNG carries it through intact.
Questions
Will the file get bigger?
Usually yes. PNG is lossless, so it stores more data. That is the trade for compatibility.
Does transparency survive?
Yes, when converting to PNG. It does not survive a conversion to JPG.
Why can't I just rename the file?
The extension is not the format. Renaming a .webp to .png makes a file that claims to be PNG and fails to open.
Can I convert back to WEBP afterwards?
Yes, with the format converter — but each lossy round trip costs a little quality.