Please help me to upgrade MacOS

Please help me to upgrade MacOS

I am running Mac OS Catalina successfully and I am going to upgrade it to MacOS BigSur. I have created a bootable USB and booting from it. On the image I want to install Bigsur on the disk named Mac. I want to clarify whether it will install a clean OS or upgrade my old version. Please help me. My previous post had been removed I don't know why. Thank you

https://preview.redd.it/1fw23r10ghs61.jpg?width=4000&format=pjpg&auto=webp&s=eed8d555c8a5bf7ab501e81d324f62684c164535

submitted by /u/selflearningdev
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