ColorSync Utility not working to convert from RGB to CMYK

I'm trying to convert some TIFF files from RGB colour format to CMYK.

I don't have photoshop on my Mac anymore so I heard of the ColorSync app and am trying using that.

I have opened the files in ColorSync and then tried 'Apply Profile' > 'Output' > 'Generic CMYK Profile' but when I save the file it still stays RGB.

When I try 'Save As' it is stuck on the dialogue box and nothing happens.

Any thoughts?

Advice would be much welcomed.