I am trying to find the name of a business by using their p o box
address.  How can I to this?

The U.S. Postal Services differentiates between private, individual
post office box holders and business post office box holders. The USPS
may rightfully withhold the identity of private individual post office
box holders, but not the identities of business-related post office
box holders. Contact the post office involved and ask them the
identity of the box holder. If the box holder is a business they
should give you the information.

In Britain, no distinction is made between personal and business
renters of P O Boxes and the renter's address is available on demand.

Owain