For the 4.0L SOHC engine, the part number is
AGSF-22F-M
You can buy them from many places, for example RockAuto, or a Ford dealer. I like this dealer, their prices are very good:
https://parts.autonationfordwhitebearlake.com/oem-parts/ford-spark-plug-agsf22fm
Please double check wether you...