Ok, hold on here. You do not need to run 2 Instances, and this might be the root of the issue you’re having.
You can have multiple databases in a single instance. This is why I do not suggest renaming the instance from SQLEXPRESS to SAMBAPOS at all. It confuses people, because many do not understand that the Instance is not the same thing as the Database.
You only need 1 Instance. Look here - I have a single instance called SQLEXPRESS, with 9 Databases…
This Tutorial shows how you can backup your V4 Database, create a V5 Database, and import the V4 data into the V5 Database, all within SambaPOS using the built-in Database Backup Module…