Hi @SinhaKislay , the upgrade process from SharePoint Server 2019 to SharePoint Server Subscription Edition is very similar to the upgrade process from SharePoint Server 2016 to SharePoint Server 2019. You basically stand up a new farm running the latest version, the mount the databases from your old farm to the new farm.
Take a look at our Upgrade to SharePoint Server Subscription Edition articles for more information and let us know if you have any more questions!
