New to film? C-41 covers most color negative film (and some chromogenic B&W like Ilford XP2). B&W is traditional black and white. E-6 is slide/transparency film. Not sure which you shot? Check the film canister or box — it'll say.
Film speed (ISO) doesn't affect your order — skip it unless you want push or pull processing (adjusting development for under- or over-exposed film). If so, note it with your order.
A few ordering rules: