What is the ruling on working for a company that transports goods, knowing that some of them may be alcohol or music tapes that are difficult to identify because they are packaged?

It is permissible to work for the aforementioned transport company unless it is confirmed that it transports prohibited goods such as intoxicants or music tapes. This is because the default for work is permissibility, and it is only prohibited by a confirmed matter. Mere possibility is not sufficient to prohibit work.