For course completion you need first to have enabled course completion. See the documentation Course completion
Please note: I will move your message to the General help forum since it isn't only applicable to MoodleCloud.
To see the activity completion report in a course it depends on your theme. You can get to it by clicking the gear icon top right and selecting "More> Reports>Activity completion" (with the Boost theme) or from Administration> Course administration> Reports > Activity completion with non-Boost themes.