I don't have a picture of the plug handy. It's not very large and it appears to have a matching yellow cap on it's end. This cap is the required resistor to keep the air bag light off. If your seats have been changed, whoever replaced them may have shoved the wire and plug under the carpet, as it emanates from a small slit in the carpeting. Hopefully they didn't clip the wire off or you'll need to find replacements at the salvage yard and solder them in.
What code is the air bag light flashing?
The yellow plastic plug has a molded hook on the end that allows it to snap onto the metal bar that runs across the rear bottom of the seats.
Here's a link with more info:
http://www.justanswer.com/ford/0uu15-2000-ford-explorer-code-36-air-bag-light-fix.html
I found this picture of the resistor on eBay:
http://www.ebay.com/itm/NEW-OEM-AIR...ash=item35e37ff40b:g:x8IAAOSwrklVTT39&vxp=mtr
Here's a picture of the wire with the resistor attached. Apparently this guy had a bad OE resistor and wired in one for Radio Shack.