The film scanner, as stated by Auldtimer, is the best way to go to get the best quality out of your negatives.
Nikon offers 4000dpi in their Coolscan V-Ed for $600 (at large dealers) and it is good value. It has a slide mount adapter. A bonus for doctors and lab people is an adapter that will take standard medical glass slides.

I started with one of those little triangular gadgets and only got frustrated by the loss of details.
Color matching in conversion is damn difficult.Tried that too and was not happy with results.

I don't know anything about the new all-in-ones coming out now, but suspect that they will give you a good, but not best, print.