How to change the Sql Server collation of all the databases (including system databases) in a given instance

Open a command prompt window and navigate to the Microsoft SQL Server installation folder in your local machine.

Then navigate into the folder created under your SQL Server instance name and then into the Binn folder.

After that type the following command and press enter.

RV7_2018: Your Sql Server Instance name.
SQL_Latin1_General_CP1_CI_AS :  Collation you want to convert into.