The original translation is wrong too.
You can see he/she used both "formato della stringa" (wrong, it means "the format of the string") and "Seleziona stringa del formato" (almost correct).
As I told you "Formato della stringa" (I used that until now) is absolutely wrong as it means the opposite of "formatstring": It's hard to translate my thoughts but it is like in English the subject is "string", in Italian the subject is "format".
It is ugly but if you want to keep a translation that sounds like the original "artificial word", we could use "Stringa del formato" (it could make think to a string that depict a format, exactly as Modello-Model or Schema-Outline/Diagram).
Sorry if I am too (WordReference says) fussy