Upgrading from SQL Server 2012 SP1 to SQL Server 2019
This handy page from Microsoft should be very useful for you as it explains in detail how to carry out a migration and the tools and methods available:
Supported Version and Edition Upgrades for SQL Server 2019

Use the Data Migration Assistant (DMA) to scan your databases to make sure they can be migrated to the 2019 server. It will highlight any potential blocking issues such as deprecated features that you may need to resolve before you can migrate.

It looks like you will still need to upgrade your SQL Server 2012 to SP4 to be fully supported though.