Why convert JPG to PNG?
PNG is lossless: once an image is a PNG, you can open, edit and save it as many times as you like without it getting worse. That makes PNG the better working format for design, editing, printing shops that ask for PNG, and assets you’ll reuse. JPG loses a little quality every time it’s saved.
What converting can and can’t do
Converting changes the format, not the picture. The PNG looks exactly like your JPG, including its background and any compression marks already in it. Photos from phones are turned upright, because the rotation stored in the JPG is applied before saving the PNG.
Going smaller instead
If you want a smaller file rather than a lossless one, convert the other way with the PNG to JPG converter, or to WebP for websites.