To find it:
1. Locate the under-dash fuse panel: This is usually found on the driver's side, under the dashboard. It's often a black plastic box.
2. Open the fuse panel: You'll likely need to open a door or remove a cover.
3. Consult your owner's manual: This is the most reliable method. Your owner's manual will have a diagram showing the fuse panel layout and identify which fuse is for the power outlet (cigarette lighter).
4. Look for labels: If your owner's manual isn't available, carefully examine the fuse panel itself. The fuses are often labeled, and you might find one labeled "Power Outlet," "Accessory," "Cigarette Lighter," or something similar. The amperage rating may also be listed (usually 10-20 amps).
If you can't locate it by these methods, you might try searching online for a 1998 Ford Mustang fuse box diagram. Many forums and websites dedicated to Ford Mustangs have this information available. Be sure to specify your model and trim level for the most accurate results.