Question about selling Vita games

My husband asked me to put these games online to try and sell for him. I was wondering if you guys could help me out with a couple things before I do so.

I am wondering what the best online platform would be to try and sell these? I’m wondering if I should do something like eBay or give Facebook marketplace a shot (I’ve never really used either to sell stuff).

How can I figure out how much each one is worth? Obviously I don’t expect him to get a ton of money for them, but I would like to try and get their worth, at least.

If anyone can help me out with some advice or suggestions, I would really appreciate it.