Hi
shinuapple89Good day! Please first provide me your current firmware version
Setting >System>About Phone>Software information
You can check on the official site for confirming which version you want to upgrade
https://www.asus.com/supportonly/ZenFone%20Max%20Pro(M1)(ZB602KL)/HelpDesk_BIOS/> For the same Android version
Check on Settings>System>System updates
>For different Android version, please try manual update
Download the file you want to update on our site in "the root directory" of the phone's internal storage. Then re-boot your phone. Check the link below
😉#[Zenfone] How to update firmware on my phone?
https://www.asus.com/support/FAQ/1009748/