If your SharePoint Server environment is not running on the 2019 platform yet, you will need to plan for an upgrade. If you are running SharePoint Server 2016, you may be able to perform a database-attach upgrade from 2016.
If you are migrating from SharePoint Server, the process is similar, but you'll need to perform a two-step migration (from SharePoint Server 2013 to SharePoint Server 2016, and then again from SharePoint Server 2016 to SharePoint Server 2019).
The following diagram depicts the high-level steps necessary to upgrade from SharePoint Server 2013 or 2016 to SharePoint Server 2019:
Depending on the size of the SharePoint farm and its activity level, organizations may also decide to opt for configuring SharePoint Hybrid environments and provisioning new workloads to SharePoint Online or migrating them altogether. You'll learn more about SharePoint Hybrid in Chapter 10, Overview of SharePoint Hybrid, while you learn more about migration...
