BCP is a command line utility with switches that are used to control the import process, including the number of rows per batch. The number of rows is not as important as the number of rows per second that are being imported.
BCP documentation and examples:
The switch to control the batch size is:
The speed of the import is affected by variables including the target table (indexes, heap vs clustered, etc.), the I/O capacity of the server, how busy the server is, the type of logging that is enabled, speed of the network, speed of the process on the client machine, etc.
I suggest you first start looking at the target table and go from there.