That’s because it won’t be called “Alsa ISB Codec”.
If the computer recognises the turntable then just restart Audacity (you need to connect the turntable before launching Audacity, or if you connect the turntable after launching Audacity, use Transport > Rescan Audio Devices).
It may not be ‘microphone’, but most likely ‘USB’. - In Linux, with a normal turntable run through the pre-amp section only of an Amp with that facility, I always use Line 0. – That works for me in Linux Mint & Zorin 7 (Ubuntu 13.04). - Rgds.