Step by Step Guide to SharePoint Migration from 2013 to 2019
Firstly, you are required to convert web application, if they are currently in the windows authentication mode, in order to claim authentication. Claim authentication is the default mode in both SharePoint Server 2016 and 2019. Next, you need to upgrade all the site collections to mode 15 from mode 14 by using the Upgrade SPSite cmdlet. For the reason that any database that will be in 14 version will be locked and prohibited from migration or upgrade to SharePoint 2016. Once, you site collections have been migrated, you are now required to create backup for all your service application and content databases from you old far e.g. SQL2013. Now, restore these databases to the SQL Server of a new farm in SharePoint Server 2016 i.e. SQL2016.
I hope these steps will be helpful!