To find it, you need to:
1. Consult your owner's manual: This is the best and most reliable source. The manual will have a diagram showing the fuse box layout and identify which fuse is for the power outlet (cigarette lighter).
2. Check both fuse boxes: If your owner's manual doesn't give a clear answer, locate both fuse boxes (underhood and interior) and examine the fuse box covers. They usually have a diagram printed on the inside of the cover that identifies each fuse. Look for a fuse labeled "Power Outlet," "Accessory," "Cigarette Lighter," or a similar description. The amperage rating might also be listed.
If you can't find it in either fuse box:
It's possible the lighter itself is malfunctioning, the wiring is damaged, or there is another underlying electrical problem. A qualified mechanic or auto electrician would be needed to diagnose such issues.