You haven't posted enough context. If you click on the Report navigator icon (the rightmost icon at the top of the left column in Xcode, which looks like a hierarchical list), you can see the full build log, which should help you to fix errors like these. With what you've posted, we can't see the name of the first missing file. The second missing file may be missing because the first is missing, and that in turn may be due to something reported only as a warning in the detailed build log.
Topic:
Developer Tools & Services
SubTopic:
Xcode