How do you convert a font file with the extension ".scr" to TTF?

The file could conceivably be a http://www.locoscript.com/ font file, or possibly an old screen font. Or it's just possible the client accidentally sent you a Windows screensaver file...

It's a screen font, and there's no way to convert it to a vector truetype font. The client will have to provide a vector file or go with another font.

Thirding old screen font. And if so, rikschell is correct... you're not going to be able to convert a bitmap font to a vector font. Out of curiosity, what is the name of the font?

The name of the font is Gotham.scr So basically there's nothing I can do with this font. Can someone please explain what a screen font is?

Way I understand it, a screen font is like a bitmap font, or a pixel font that was so popular with designers a few years back. It's basically just a font that's defined by where each pixel is, so it's limited entirely to one size (or a handful of pre-defined sizes) to be displayed on a monitor using that amount of pixels. You can't scale it up or down to any point size you like which makes it nasty for printing. But if it's like a pixel font, I figure you could set a normal point size, say 10 or 12, and have the screen font map to that so that it looks the same. It'll just look strange and uneven if you try to set it at any other point size. I have no idea how font conversion works or even if there's an easy way of doing this. But people have made vector-based TTF files that basically behave like, or is meant to be used as screen fonts, so...

But people have made vector-based TTF files that basically behave like, or is meant to be used as screen fonts, so... The purpose behind the invention of Truetype was to obviate the need for separate screen and print fonts. So when you see Truetype fonts that work well on-screen as well as in print, that's the whole point. http://en.wikipedia.org/wiki/Computer_font But if it's like a pixel font, I figure you could set a normal point size, say 10 or 12, and have the screen font map to that so that it looks the same. This is true for doing work that is only meant to be shown on-screen. If you tried to print this hypothetical work, though, it would look jaggy and bad or default to Courier. You have one piece of all the files necessary to use this font in a regular way. Some programs won't recognize an incomplete font set at all, and will simply ignore the font. I bet it's not worth too much more effort trying to figure out what you can do with just the .scr file. Ask for a Truetype version if you're in the position to ask somebody for something, buy the font, or choose some other face.

To answer the question in your headline directly, I don't think it's possible to convert an .scr to a .ttf. There's just too little information in the .scr to make a complete character glyph set for printing.

Maybe search for a similar font in your library or see if the client would be willing to buy one (Is it http://www.typography.com/fonts/font_overview.php?productLineID=100008? It looks nice.). Otherwise, just tell them that you won't be able to reproduce it and that they need to choose a different one to replace it with.