Cr(CO${_3}$)${}_3$
This is an ionic compound. Chromium is a transition metal cation and CO${_3}$ is an anion with a charge of 2-, as said in my chemistry textbook.
And since CO${_3}$ has a charge of 2-, the over all charge of CO${_3}$ would be 6-, since it has a subscript of 3 in the bolded formula above. So my guess is that since Chromium has no such subscript, its charge would automatically be 6-, which should be right because it would cancel out both charges.
Therefore it would be Chromium (VI) Carbonate? Please correct me if I am wrong.