What's best for converting old .SWF & .FLV files to .MP4
 

I've got some old material that I can use in current project. I've tried the online media converters but
I'm getting the sounds and not the actual video in the conversion.

https://handbrake.fr/

Free, & simple enough for me to understand :) You set up what you want and then you can instantly do it again using the same settings in the future.

Works on Windows, mac and Linux :thumbsup