I'm really scared about work experience?

I am 15 and working at an Architects and i'm not really too sure what i'll be doing! Do you know what kind of things i'll do? Also I don't know what to wear! The dress code is smart casual, so I was thinking leggings and a shirt? And for lunch I think I have an hour (not too sure what time), I mean for lunch will I go outside of the workplace or stay in that building? Shall I bring a pack lunch? Or shall I just go into a Cafe and have lunch on my own? SO sorry for all the questions! Thank you so much if you answer this!