I'm sorry to hear that. If you give us a little more information, we might be able to help you though.
When you import photos into Tropy, it generates thumbnails for them, but does not alter the original photos. When using Tropy in the project view, you should see the photo thumbnails; when opening a single photo in the item view, Tropy will load the original photo. If you've moved your photos after importing them, this is likely the reason why they disappeared. In that case, don't worry, you can consolidate the photo library by right clicking on each photo and selecting the photo again from its new location.
If this affects all 200 pictures in your library, and if you've moved most of the photos to the same new location, we can help you update your project database in one go. Please see this thread for more information.
If you have not moved your pictures, please start your Tropy project again, try to open some pictures and then select Help -> Show Log Files from the menu. If you upload main.log and project.log here it might help us understand what's going wrong.