Hello bbgreene, If you’re running any release from macOS 10.13 (High Sierra) to 10.9, you can upgrade to macOS Big Sur from the App Store.
Supported hardware for Big Sur.
MacBook (2015 or later)
MacBook Air (2013 or later)
MacBook Pro (Late 2013 or later)
Mac mini (2014 or later)
iMac (2014 or later)
iMac Pro (2017 or later)
Mac Pro (2013 or later)