my employer wants me to contact a former co worker who commited fraud to try and have a sit down and attempt to settle case. I don’t want to get involved. Do I have an obligation to my company to do
No, It's up to you whether you want to involve or not. An employer can't force you to do so.
You're obliged for only the job you were fired for. Still, if you think you can help your company with something, you must give it a try.