Answer by Professional Japanese Teacher
Congratulations on starting a new internship. Since you are going to meet your colleagues and superior for the first time and this is a formal setting, it is best to use the full version “ohayoo gozaimasu” to be more polite.
If you have become close to the person, you may drop the “gozaimasu” and use the casual version “ohayoo” to sound more friendly. For more essential greetings in Japanese, check out our following article.
8 Essential Japanese Greetings for Japanese beginners