SWF to Premier???

Open the project file (FLA) that created the SWF in Animate and then choose File > Export > Export Video/Media.

I recommend setting the Format to QuickTime and setting the Preset to Apple ProRes 422 LT and then set the Sequence Video Previews to ProRes 422 LT as well in Premiere Pro; however, ProRes 422 and ProRes 422 HQ are also good choices.

I find it helfpul to have Adobe Media Encoder already open before clicking "Export" in Animate.  

This works best for non-interactive animations.

you won't be converting a swf in animate.

import the swf into after effects and save the project and then import that ae project into premiere.