Japanese: What does the particle "mi ni" mean?

As in "みに来る" (mi ni kuru)? I've also seen "mi ni iku"? I'm familiar with "ni" but the "mi" stumps me. And if you have extra time, I'd also really appreciate it someone could explain any of those other weird combination particles such as "na no ni" "no wa" "ni mo". And " じゃ" (ja) what does ja mean? It's used quite often in Ja'nai and I understand that but I've also heard ja by itself.