Black Diamond Question Mark in XML

I'm getting black diamond question mark's, and need to convert them to apostrophe's instead:

Here is my code I'll use, but what would I put for the black diamond question mark in replaceOccurencesOfString?

[temp_str replaceOccurencesOfString:@"" withString:@"'" options:NSLiteralSearch range:NSMakeRange(0, [temp_str length])];

I'm doing an iPhone app in Objective-C.