I am looking for an adaptor for my HP laserjet 4ML printer which has an 8 pin serial connector and I want to connect it to a computer that uses usb connections.

My HP service manual indicates the 4ML came with Apple LocalTalk and parallel interfaces. A cursory Google yields numerous parallel to USB adapters. Don't see any LocalTalk to USB. Aante offers a LocalTalk to Ethernet bridge. Since my Mac knowledge is limited, also suggest you post a question in the Apple/Mac forums.

Resources:
USB Capable Macintosh: Connecting Serial, LocalTalk, or Parallel Devices