Use the following instructions from this discussion however instead of Strive for Power's .import, use Strive: Conquest's .import:
https://itch.io/t/1990896/importing-strive-for-power-characters
As for the PNG files itself, unfortunately haven't seen an online converter, you'd need the original PNG files or import it to Godot and export it out as PNG.
I'm not sure if the devs allow using it for outside their games however it's up to you. Good practice is to ask first~