Windows 10 current, Publisher 365 also current.

A leaflet designed in Publisher is by default RGB. Printing company prefers CMYK.

I have looked for a means to design or convert to CMYK but what I have found seems to relate to older versions of Publisher. What I did find, but again I can't see the CMYK options, is this
https://support.microsoft.com/en-us/...7-abddeeb044ff

Any help would be appreciated.