HELP ASAP? What to wear to a marketing job interview?

Im 18 and vie got an interview as a sales advisor at a marketing company TOMORROW. They said to arrive 'smartly dressed'. I don't want to look like im going to school. I have a grey formal dress but it shows the tattoo on my arm. All the tattoo is writing on my arm. Ive got a white blouse with frills and a plain black bow and a pencil skirt. WHICH ONE? Or should i choose something else.