That’s a bit odd. Possibly it’s not an official version you have and something that has been modified (V3 is open source after all so it is quite possible).
This forum is meant for V4 and V5, however what you need to do will be same in V3 so its fine. You are using SQL Compact Edition database (CE). You will need to download “SQL Server Compact Toolbox”
The tutorial below is not related to this, but you can follow the steps how to download the tool and connect it to your SambaPOS database. Follow the steps in this tutorial from the part that says “Screen shots for exporting SQL CE data to SQL Server Express”
After you got to this step:
Expand the database tree and you should see a “Users” table. I don’t have the tool installed but if you right click the Users table you should get some options one of which will be to SELECT rows, that will display the contents. You will see the username and password for each user stored there.