Translation and explanation

I try to practice my Japanese via email with penpals. This sentence I didn't quite understand.

日本へは何をしにくるのですか？

Obviously, it has something to do with Japan and the question is imposing "what". The part that is really throwing me off is the "しにくるの". Can anyone:
1. Translate the sentence and
2. Give me an explanation as to what is grammatically going on with that section I pointed out.
Thanks!

This means "what are you coming to Japan to do?" or "what do you plan to do in Japan?"

し is part of the verb します, "to do", に is a particle, and くる is the verb "to come",
so "shi ni kuru" means "come to do"- the order in Japanese is obviously the reverse of the English.

"Mi ni kuru" would be "come to see" from the verb "みます”.

Does that make sense?

As explained already, this "ni" is the "...ni" indicating a purpose.

[・・・]に　くる/きます = come for the purpose of [something]
[・・・（を）　し]に　くる/きます = come [to do (something)]

Your answer might be something like:
[かんこう]に　きます。(I will come for sightseeing) "kankou" = sightseeing
[べんきょう]に　きます。(I will come for studying) "benkyou" = study
[日本ごの　べんきょう]に　きます。 (I will come for studying the Japanese language.)

You could also say the "I will come for studying" sentence as follows, using the "to do..." construction:
べんきょうを　しに　きます。 (Literally, "I will come to do studying.")

Thank you both for the in-depth explanation haha. I guess I was over-analysising the sentence a little bit because it was not so complicated -_-. Regardless, thanks again!