Any upDates to High Sierra stopped somewhere in November 2020. If you what to upGrade that is a different matter. Check over here on How to get old versions of macOS. Moving from High Sierra to any newer version of macOS will be totally governed by the Age of the computer. Once you determine age of machine via About this Mac on Apple Icon Desktop - choose the version the qualifies for. Make a Time Machine Backup Before attempting.
Note: The links in next page Must be opened in Safari as Others may not work. Safari will open a redirect and open Apple Store to commence the Download of the Full Installer. 2nd Note: Staring in Catalina and above - neither os Supports any 32 bit Application / Extensions / Drivers Only 64 Bit is supported. 3rd Note: Are there any AntiVirus, Disk Cleaner, Optimizers, Defrag, VPNs etc installed which should be removed as per Developers Instructions. They are useless, unneeded, cause havoc and interfere with the normal operation of the OS. The Built-in Security of Big Sur is all that is required.