If you delete creatives, you can't get back the same creatives. However, you can create new creatives with the same data if you use the "+Load From Library" button in the pop-up where creatives are added to the campaign.
You can select the ad account that the creative belongs to and you can search for the name of the deleted creative to find it faster. If you favourited the creative before, you can see the creative at the top of the library. If your creatives have the same name, you can simply click on "Preview" to see the content.
In order to use the creative, all you need to do is to click on the "Use" button and the new creative with the previous settings will be added when you save the changes.
Note: You can get the data of the deleted creatives in the Metrics tab if you choose the "Status" column.