In the Key-in window, key in: MDL LOAD batchconvert -nodialog <batch_conversion_job_file_specification>. For example, MDL LOAD -nodialog C:\ProgramData\Bentley\MicroStation CONNECT Edition\Configuration\WorkSpaces\Example\WorkSets\General\my_conversion.bcnv

The Files to Convert dialog opens. At this point you can click Convert to start the job or Cancel.