The change in the UI between 7 and 8 is quite significant, as you might expect. Are you able to share a screenshot the applications that you can see in the admin section?
It may be that the modules themselves are either not installed or not configured to you current user. Try these two things:
- Open the modules application and check that the modules that you need address setup and assigned to your site.
- check that your user has permissions to use those modules. The chances are that you're a global administrator, but still best to check the permissions.