Read the error message, it's pretty clear:
foreach statement cannot operate on variable of type 'produto' because 'produto' das not contain a public instance definition of getenumerator
Include the IEnumerable interface in your class definition, and implement the required method (GetEnumerator)
IEnumerable Interface (System.Collections) | Microsoft Docs[
^]
Only if it supports IEnumerable can a class be used as a collection for
foreach<code> loops