How do I prepare myself and be less worried for my new job?

Hello, I'm 16 years old. My old job was terrible. I worked for a big privately owned corporation, they were all mean and just terrible. I'm starting a new job at a smaller boardwalk candy shop this Friday, and I'm really nervous. They're having me work for 2 days, then they decide if they like me. I'm also really nervous they may not like me because I'm unsure how to do a few things, and the owner is aware of this. How to I become less nervous about starting? I'm afraid it will be a rerun of my last job. How can I prepare myself? Thank you!

I used to research beforehand the place and the position. By getting as much information as possible helped prepare me as to what to expect. For things I didn't know or were unsure about there were usually sites or videos which turned out to be helpful. I also would prep clothes/uniform and any other essentials I may think I may need and have ready. Mentally I would create scenarios that can arise and possible solutions. Pep talks help. Music to calm you or inspire you. Or whatever relates to you. I pray. As far as people go.... You meet all kinds in the world of work. I try to be considerate of people I come across. My settings require me to be firm but polite else they will eat you alive. Actually the polite is just me but channel your confidence, keep an open mind and simply do your best.