you can help me update my MacBook Air on Mac OS Big Sur on App Store please

Please read all the information on the Apple How to Upgrade to Big Sur. Be sure the computer is compatible as per their list, and have enough empty space again as per their instructions. Also, Before attempting the upgrade, make sure you have a Time Machine Backup and if possible 2 Bootable Clones each on separate external drives ( Insurance incase thing go side-ways).

Good Luck

Hey there!

There are some steps over at How to upgrade to macOS Big Sur – Apple Support which will help you upgrade to macOS Big Sur.

Let us know how you go!