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By doing the Konami code, I got this message. What's written?

I can't translate, but I can transliterate, at least, if it helps:

konotabi wa, KONAMI no
T.M.N.T.2
- THE MANHATTAN PROJECT -

o, okaiageitadakimashite,
makotoni, arigatougozaimasu.

このたびは、コナミの
Ｔ．Ｍ．Ｎ．Ｔ．２
ー　ザ　マンハッタン　プロジェクト　－
を、おかいあげいただきまして、
まことに、ありがとうございます。

According to The Cutting Room Floor article Teenage Mutant Ninja Turtles III: The Manhattan Project, it says "We are truly grateful for your purchase of T.M.N.T. 2: The Manhattan Project by Konami."

rainwarrior wrote:このた　は、コナミの
Ｔ．Ｍ．Ｎ．Ｔ．２
ー　ザ　マンハッタン　プロジェクト　－
を、　おかいあげ　いただ　きまして、
まことに、　あいが　とうご　ざ　います。

1. Taking out all the spaces and enters, Google Translate says "This is T. Konami. M. N. T. 2 - The Manhattan Project - We are truly grateful to you for your support."

2. Using just the first half of the message, replacing the game name with X gives "This is Konami's X"

3. By combining both attempts, I suspect it means something like "This is Konami's T.M.N.T. 2 - The Manhattan Project - We are truly grateful to you for your support."

You almost got it, but you missed the "bi" in "kono tabi", mistook the "ri" in "arigatougozaimasu" for an "i", and also the spacing is a little strange dividing words in half.
It should be:

このたびはコナミの
T.M.N.T.2
- ザ　マンハッタン　プロジェクト　-
を、おかいあげいただきまして、
まことに、ありがとうございます。

Kono tabi wa Konami no
T.M.N.T.2
- The Manhattan Project -
wo, okaiageitadakimashite,
makoto ni, arigatougozaimasu.

Cutting Romm Floor's translation is correct.
"On this occasion we truly thank you for purchashing Konami's T.M.N.T.2 - The Manhattan Project."

It's the typical formal thanking message that you often see in the beginning of the manuals for games.

Ah, thank you for the corrections. I'm realizing now that the spaces were an error too, just a consequence of the dakuten in a monospaced font.