I don't have this mod myself, but generally speaking: The units animation-files (.flc) are defined in the pediaicons.txt. Search for "Italian Halberdier" here, and check the entry that looks like this:
#ANIMNAME_PRTO_units name
Italian Halberdier
The name must be an exact match in three places: In the pediaicons.txt-entry mentioned, the unit's folder name, and the name of the .ini-file within that folder. If any of these have an extra space or some other differences, the game will give you an error-message like the one you got. So I would suggest that you check that there aren't too many or too few spaces in any of the names.
See also Wolfshade's answer above.