remove.bg is a free online tool that removes backgrounds from your image and returns it to you in a .png format.
It works pretty well, but the maximum height or width will be a low-ish 500 pixels and the other dimension will be proportional. If you’re viewing this on a desktop or laptop, you can see how the image breaks down at larger sizes. It’ll be good for social media posts in Adobe Spark, but probably not your next trifold.