How to search custom fields

So the stores on our site have protected franchise territories, meaning they each service certain zip codes. We added a field with a list of all zips they work with (comma separated) to each store. For most stores, this isn’t an issue since they’re further away. However, in the New England area, some stores are close to each other and their territories run up against each other. One store may have one zip, while a farther store has the city next door, despite the store being farther away.

How can we utilize this plugin for our issue? Everything else it does is great, and works for most of what we need.

Thanks!