Hi @Karl17, good question! The social media icons in SquareSpace come up as .svg files (they're code files that serve as images, but are not technically image files like a PNG or a JPEG): https://www.sitepoint.com/svg-101-what-is-svg/
Have you thought about screenshotting the icons, removing the background, and then importing them as images onto your website? Or perhaps, you can save them from Google and then import them onto your site?
Pixabay has a number of license-free social media icon libraries if you're looking for social media icons: https://pixabay.com/images/search/social media icons/
Let me know if this is helpful or if you have any more questions I can help answering!