Please help me quickly get my vitamin levels up

Hello!! I'm a 19 year old girl about to hopefully join the US Army, which is my dream.

However, considering my diet consists of (and practically has ALWAYS consisted of) dino chicken nuggets and cookies, I'm quite worried about how I can quickly get my vitamin levels up and whatnot. I've started taking women's Centrum vitamins recently, but is there anything else I can do? I'm so so nervous about this.

So, I’d really appreciate ANY advice you can give me. Like what foods I could eat or anything. I would really appreciate it. This is my dream job. Thank you!!!