You can find surveys, questionnaires, and interview questions through some of the research articles you may find in EBSCO. ProQuest, or Google Scholar. However, sometimes, if you Google terms like "gang prevention programs" AND evaluation, you may find sources that either were not full text in EBSCO/ProQuest, or weren't included. In some cases, the citations will be included, but the instrument may be behind a paywall. You can ask a librarian on the easiest way to obtain the instrument.