Are you sure this is the right thing to do, because the print shops I worked with in recent years all don’t even want CMYK files anymore, they either want RGB or have their own Color Profile you need to proof against. Normally nowadays you work in RGB only, use soft proofing to check your stuff in CMYK (you can set up soft proofing in Krita) color space and only convert right at the end (or not).
We actually have many topics about this on the forum, this is one of them:
One of the reason is that industry printers don’t even work on CMYK anymore, they often have more than 12 different colors to make up for the colors CMYK can only mix badly.