I am having a very hard time trying to get the color turquoise . When converting from rgb to cmyk they are nothing close. How do I get the color of turquoise I see on my monitor to be printed on cards? What is the best method to see the conversion on my monitor?
Yes, that's what happens when you convert the brightest of RGB blues (#00ffff) to CMYK for printing. The dramatic change is because it's outside the CMYK colour gamut - in essence that means it's an unprintable colour. So the short answer to your question is it's not possible to get the bright turquoise you see on screen to print on a card.
You'll need to choose another CMYK colour that's closer, but there is no way that it will ever be as vivid as a pure RGB #00ffff, because there is no ink on this planet that is as bright turquoise as that.
The brightest most vivid blue available in CMYK is probably 100% Cyan - but pure cyan is darker than RGB #00ffff - you could lighten it by using less cyan and a touch of yellow.