You have 2 options, so use what is easier for you:
1. There is a Search Everywhere top right of admin.
Type in there word model and wait for auto suggest or hit enter (search) to get full list
look for the result for product_product and storefront. Click and edit.
2. Go to System -> Localization -> Language Definitions
Type model in Translation field of the grid and hit enter.
Filter result if you want and click edit.
NOTE: This is version 1.1 and later