Does K3b convert .uif to .iso?

The short answer is no.

There is a windows program that will do this that runs in wine quite well. See http://ubuntuforums.org/showthread.php?t=482960 for how to install it. Heres the post copied into here:

The only way i know to convert that format to iso is to use magiciso with wine on linux.

Basically the dummy steps are:
Code:

sudo wget http://wine.budgetdedicated.com/apt/sources.list.d/feisty.list -O /etc/apt/sources.list.d/winehq.list
sudo aptitude update
sudo aptitude install wine

winecfg
wine "path to magiciso installer"
wine "path to magiciso.exe"

Do note that wine is quite a big software altogether and you might want to read more about it before trying my instructions.

but magiciso cant convert bigger than 300mb without a serial

At least you can extract the files from .uif with magiciso without any serial

I found the solution to convert the uif file into iso.

http://wiki.linuxquestions.org/wiki/CD_Image_Conversion#uif2iso

Simply download the tool, extract and change into the folder. There you type to install:
$ sudo make install

And from now on you can use the commandline to convert .uif files as follows:
$ uif2iso input_file.uif output_file.iso

Done!
:-)

You can check <a href=http://www.teseter.com>Ubuntu .uif converter</a> for some info and links regarding .uif images