@eyesofmint this is to augment the excellent answer my esteemed colleague already left. The USB port is soldered to the CPU board. In the attached image #10 is the USB cover and if you follow the dotted line, you recognize the outline of the USB connector.
[image|2733161]
Now, to get to the board, the disassembly part of the service manual for your Singer should help you with that. [document|27631]