Hi Christiekhall,
Welcome to the Apple Community, where some of us do our best to help each other :)
It seems that not all Macs can / do update from the App Store.
First you might want to check the model (Year) of your MacBook Pro
Once you check the Year (from "About this Mac"):
You can scroll down to the correct MacBook Pro Model,
and find out which versions of the Mac Operating System are suitable for your Mac.
Here's the link to help you:
Identify your Mac Book Pro model
https://support.apple.com/en-us/HT201300
If your Mac isn't compatible with the latest macOS, you might still be able to upgrade to an earlier macOS,
such as macOS Catalina, Mojave, High Sierra, Sierra or El Capitan
If you can update to the latest (Big Sur) version: here's how
https://support.apple.com/macos
OR
How to get earlier versions of macOS
https://support.apple.com/en-au/HT211683
Hope this helps you :)