Girls, 18 weeks pregnant, I still don't know if it's a boy or girl, th…

Girls, 18 weeks pregnant, I still don't know if it's a boy or girl, the second ultrasound is only on the 20th, I want to go to a private one tomorrow and take my husband with me so he can see everything. When I book an ultrasound appointment, what should I say? Do I need a second ultrasound or what do I need? ? In a general clinic they know what to look for based on the referral.