The whole idea behind Prezi Next was to move away from Flash based technology, so uploading an SWF file directly into Prezi is not possible anymore. However there is an easy workaround and you can still use your existing SWF(non-animated) files in Prezi Next.
The solution is to convert your existing SWF files into SVG format, which is now supported by Prezi. If you have access to Adobe Illustrator or Animate, then you can make the conversion in these softwares, but there is also a free online option. We tested many online tools, but found the easiest Riaxe converter – A free tool which allows you to upload your SWF files, preview them and then export into an SVG format.
The downside is that your SVG files will not be zoomable inside Prezi Next. For zoomable graphics it is necessary to convert your SWF files into PDF, however we couldn’t find an easy and free online service that could provide this kind of conversion.
Migrate entire Prezi Classic presentation to Next?
If your ultimate goal is not just to use one SWF graphic, but to migrate your entire presentation into Prezi Next, then is a tough challenge. Prezi does not offer any kind of option to transfer your content. Although transferring content from Classic to Next seems to be the most debated topic on the Prezi forums, then it currently seems there is no solution for it. We just have to hope that very soon Prezi will roll out a new feature which allows 80 million Prezi classic users to migrate their old content into Prezi Next.