You didn't provide much of the information that would be needed to help you. For example:

what Mac hardware (including any external monitors) and macOS version? SketchUp can become confused about where to place dialogs if you use monitors with different resolutions. Also, there is no guarantee the SketchUp 8 will run correctly on newer versions of macOS (though it might...). where did you obtain the copy of SketchUp 8? It has not been available directly from Trimble for some years, and who knows whether the one you obtained is intact... does any part of SketchUp 8 work correctly? Said the other way, are these dialogs the only issues you encounter?