Open C:\ProgramData\SAMBAPOS\SambaPOS5\SambaSettings.txt
Where you see C:\Users\adminSambaPOS5.mdf change it to C:\Users\admin\SambaPOS5.mdf then save the file. Try and start SambaPOS and see if that works.
On another note, it’s highly recommended one uses SQL Server. The Express version is free. For Windows 10 SQL Server Express 2017 should do.