First Ultrasound coming up

First time being pregnant, I am wondering what should I expect in my first ultrasound. I am going next week and I am going crazy and doing a lot research. I have started my prenatal a few days ago. I had a regular dr visit and she wrote me which one I should take, as well as i am below normal in iron levels. After the ultrasound I have lab work, can you all also tell me what do they usually check on that appointment. I really appreciate everyone’s help.