Hi @Louisa_Trunks, welcome to the Community Forum!
The “Deleted Items” view allows the person whom created or deleted the task, subtask, or Conversation to restore it within 30 days.
If a project is deleted, all Project Members will receive an email notification of the deletion and the person who deleted it will receive a link to undelete it, if they so choose within 7 days.
I also recommend you to check more information shared by our community members in these threads:
I hope this helps!