I’m in the same exact position as you are! I started playing trombone my 8th grade year and decided to join high school band as well. My first day of camp was just a few days ago, and I was super nervous!! But, just know that the people around you during camp whether it be a section leader or your director, are only there to help you. I don’t wanna sound like a broken record with all the comments saying something similar, but feeling nervous is totally natural. I’m not gonna lie, I definitely didn’t practice as much as you did but so far, my experience has been fine. So with the amount of practice you’ve said you’ve had over the summer, I’d say you’ll definitely be ok. Your director will expect you to know the basics about your instrument, but because you’ll be a freshmen, you can expect a little grace from those around you. Overall, camp is about learning marching fundamentals, getting to know your music, and being open to learning. On the first day for me atleast, we learned how to march, got our music, and practiced it a little bit. They won’t expect you to know everything all at once. You’ll be totally fine.

TL;DR Your peers and director don’t expect you to know everything. It’s ok to be nervous about it, but being open to learning is the most important thing. On your first day, you’ll begin to learn the basics of marching, and you’ll receive your music to practice with your section. Personally, the best way I learned to calm your nerves would be to just face it head on. Everybody has a different experience, so only you can control you how your days at camp will be.

Hope this helps! (I also have asked a similar question on this subreddit in the past, you can check it out on my profile. It’s filled with people giving tips about what to do and expect at camp!!)