Inside that PDF, you will find the exact diagrams for the N15235 motherboard. Look for sections labeled:
If you have landed on this page, you are likely holding a Dell OptiPlex 3020, 7020, or 9020 (Small Form Factor or Micro Tower) in your hands. You have searched for the — a specific alphanumeric string printed directly on the PCB (Printed Circuit Board) of your computer. n15235 motherboard manual