Which version of the MLA manual are you following? The new 3rd edition does not provide for any special footnote format, so citations in footnotes should look just like citations in the text.
If that is what you want, open the style for editing. Go to the Footnotes>Templates section of the style. Look for the “Format citations in” option, and use the drop-down menu to select “Same as citations”.
We have an output style for MLA 3rd edition available for download on our website.