I am currently working on a Turkish language pack for all of the expansion/stuff packs and the base game. However, I really do want to use letters Åž, Ä°, Äž and ÅŸ, ÄŸ --- ÅŸ and ÄŸ always comes up as _
I want to edit the font myself so using those letters is possible. Can you tell me or guide me where are the font files?

I created a topic earlier on the EA forums and someone said that the fonts were located in The Sims 3\Game\Bin\Resources. I edited them to include my Turkish letters, however, no luck. I deleted them and the game ran just fine. I noticed that the fonts there were for the Launcher!

I need to access the in-game fonts. I need to edit them. Most of the fonts have ö ç ü and ı but ş and ğ are missing. I need complete control over the fonts and letters. Can you help me out? Please?

Anyone?

Have you tried asking in Modding Discussion? http://www.modthesims.info/forumdisplay.php?f=547
It's possible that someone who hangs out over there might know. (Also, anyone who comes in via the front page and is set for Sims 3 will see your question, rather than waiting for them to check over here in Help.)