Explanation
The argument name that follows UiPath best practices for argument naming conventions is out_ConfirmationNumber. According to the UiPath best practices, the argument name should be meaningful and include an indication of its type and direction. The type can be inferred from the argument's data type, such as String, Int32, DataTable, etc. The direction can be one of the following: in, out, or io. The in direction means that the argument can only be used within the given project. The out direction means that the argument can be used to pass data outside of a given project. The io direction means that the argument can be used both within and outside of a given project4. The argument name should also follow the camel case convention, which specifies that each word in the middle of the argument name begins with a capital letter, with no intervening spaces or punctuation5. For example, the argument name out_ConfirmationNumber follows these best practices, as it indicates that the argument is of out direction, and that it stores a confirmation number value. The other argument names do not follow the best practices, as they either use incorrect or inconsistent prefixes, or do not use camel case convention. References: ST-NMG-002 - Arguments Naming Convention and Variables, arguments and workflows naming - best practice from UiPath documentation and forum.