New to Model RR Trains

A long while ago, I inherited some of my father's old Lionel railroad trains--an old black engine, a black coal car, an orange carrying car, and a red caboose. I'm relatively sure it's O scale based on the size. I do have a few tracks but not many, and there is no transformer left. Anyhow, I've been really getting more and more interested in putting together a model train set and I'm wondering if these trains will even work. Is there anyway to figure this out?

I'm also wondering if the train doesn't work if it would be cost-efficient or even possible to try and get it repaired? I'm more inclined to go with O Scale simply because I'm into tabletop wargaming and the scale is 28mm which is 1. what I'm used to work with and 2. would probably look better alongside an O Scale train.

Anyhow, just wondering what your thoughts are? Thanks!