Firefox has nothing to do with what is put into your inbox, your mail adress likely got captured or hacked.

Make sure you have a good password and you change it.

Mozilla or Firefox isn't leaking information about your location. That information is available via normal HTTP protocols so that whatever information you request goes to your device and your current IP Address. Click a link to go to a website and that website needs to know where to send their webpage. And if you are a member of a social networking website, and you have "cookies" saved for that website, it isn't all that hard to figure out who you are by another website. As far as how that information gets into an email sent to you, I have no idea - unless you are using an email account connected to a social networking website or you have "leaked" too much private information. Plus, I honestly doubt those emails are from real women; I think "someone" is misusing location data as a form of exploitation for attempted profit.

As far as prevention - are you using a wireless connection - Wi-Fi?
Or a hard-wired connection?

When you're using Wi-Fi, even at home, your location can be pinpointed more exactly then when using a hard-wired connection. Wi-Fi location data is collected by not only every damn Smart Phone out there and sold to various entities by the cellular service providers, but also made available from Google who collected that data with their Street View cars. Even if you would change your Wi-Fi user name, you still might be able to be located via other Wi-Fi signals in your area.
Your location when using a hard-wired connection is more approximate, but X-number of miles away can be determined to within maybe 4 blocks of your real location (when you are located in a metropolitan area), based upon information that most broadband providers make available to anyone who pays for that information. My cable internet provider used to show my location 10 years ago as their service office where they connect to the internet, like 4 1/2 miles from my home. About 5 years ago my location was like 1/2 the distance closer to my home, and now it is like 3 blocks away.
If you are paying for a fixed IP Address it might be possible to pinpoint your location to a specific street address, I suppose, if your ISP has sunk that low.

If will answer what types of connection that you typically use, someone here should be able to give you more information, as to preventive measures.

It's unlikely that any junk emails actually are personalized to your location. They probably said the same thing to all the thousands of guys who got that message. And that's not their real picture. ;-)