To be sure, I recommend:
* Consulting a repair manual: A Haynes or Chilton manual for your specific year and model Transit will have diagrams and instructions showing the pump's location.
* Using online resources: Search for "1998 Ford Transit windshield washer pump location" along with any specific sub-model details (e.g., "1998 Ford Transit 250 windshield washer pump location"). You might find photos or videos from other owners who've replaced their pumps.
It's best to visually inspect the area behind the bumper in both wheel wells before undertaking any repairs. Be prepared to get a little dirty!