You don't need to have any data in the table to generate a format file. To generate a format file you need to specify the format keyword. So it should be something like this:bcp YourDatabaseName.dbo.temp format nul -f .\datafiles\temp.dat -S ACER-PC\SQLEXPRESS -U sa -P sa
But, couple of things:
1. The above statement will generate the format file in plain text format. Usually I prefer XML - it is easier to read and edit.
2. I almost always also specify the -c option so I don't have to provide the format information for each column while running the bcp command.
So, I would prefer:bcp YourDatabaseName.dbo.temp format nul -f .\datafiles\temp.dat -S ACER-PC\SQLEXPRESS -U sa -P sa -c -x