Several posts from others who have attended Pre-Knob visits can be searched on this site, either this or the ROTC forum. If you are an accepted applicant, you should receive a packet of information that includes your agenda and also appropriate attire. If you have not received this call the Admissions Office. What I have read is kacki slacks and shirt should be fine. Below is a previous post: Preparing for Pre-Knob Overnight NEXT WEEK! Help?
You should be able to log in to your application account and find a packing list, or go back and look at the email they sent you verifying your pre knob visit. The packing list was on there."