OpenFl has “some” support for SWFs, but the key limitation is that it doesn’t support timeline code. It should support your old IDE SWFs fine.
Other limitations are: no shape tween, no motion tween (only classic tween), and it’s worth noting that complex vectors tend to have poor runtime performance so it’s advised to simplify and to use more bitmaps on the timeline.
https://www.openfl.org/learn/haxelib/tutorials/using-swf-assets/