Export data from non-relational database from 2003 to a new ASP.NET MVC 5 relational database

We have a really old non-relational database (MSSQL) and ASP.NET app from 2003 with a bunch of data.

We want to export this data and import it into a new relational database based on ASP.NET MVC 5 and Entity Framework. What is the best approach for this?

We're thinking an XML solution where we first export the data from the old database, create an XML-document, we add the data to this XML-document, parse the document and then use the XML-document as a source for importing the data into the new database. It is also worth mentioning that the old database will continue to be operational and will get updated with new table rows once or twice a day. These new rows will have to be exported and imported into the new database through a scheduled task in Windows.

Are there any other (better) alternatives for continuously exporting and importing the data daily?

Another solution would be to directly export and import the data between the databases without using an XML-document in between.

The third option I can think of is creating an API for the old database that the new database can talk to through the MVC 5 app.

What is the preferred alternative here?