You will likely first need to configure a Linked Server in SQL Server that can connect to the Tableau Server. Then you can refer to objects in it, like they are in another SQL Server.
Tableau server seems to use PostgreSQL to store data. If that's the case, you should be able to follow standard instructions for creating a linked server to PostgreSQL. Here's an example.
Make sure you can run T-SQL queries in SSMS (connected to SQL Server) to get the data.
Then you should create a SQL Server Agent job that runs on a schedule, and executes the commands to copy the data from the Tableau Server to SQL Server.