I have a piece of art I would like to turn into a print for a nursery, but when most sites require a tif or jpg format. When I change to tif, my preview looks odd, it shows everything on the pasteboard, not just my artboard. How do I fix this?

I want to turn a piece of art into a giclee printing, but am having problems getting the correct colors in the preview (is the preview incorrect?) and the format is wrong I think...When I uploaded the file to the printing service site, they wanted a tif, but didn't ask for the jpg too.  Please help, this is my first time!