How should I dress when visiting Orthodox Jewish family?

I have a job providing early childhood services to kids with special needs in their homes. My new client is a toddler whose family is Orthodox Jewish. My supervisor informed me to "dress modestly" when making my weekly visits. Can anyone give me more details? Do I need to wear a skirt? Cover up my elbows? I really have no clue... I have SEEN Orthodox Jewish people in my town so I know how they dress themselves, but I have no clue what I would be expected to wear when I go to their home.