Welcome to ecomodder.
You can easily convert between L/100km and mpg by using some online conversion tools like
Online Conversion - Fuel Consumption Conversion
(They offer many other conversions in the pull-down menu on the richt side.)
The online fuel consumption / car costs logging website
MPG and Cost Calculator and Tracker - Spritmonitor.de also allows conversion between L/100km and MPG of the fuel logs.