Welcome to the community!
Permanently deleted boards can't be recovered but still have a look at these articles/documentations
Archive & delete a board: https://help.trello.com/article/801-deleting-a-board
Archive & delete a list: https://help.trello.com/article/786-archiving-lists-deleting-lists
Archive & delete a card: https://help.trello.com/article/795-archiving-and-deleting-cards
If perchance it's just closed, choose Boards in the header, then select 'See closed boards' at the bottom of the Boards header menu and you can find it again...
But If you closed the board, then pressed the 'Permanently Delete Board' sadly, the board is permanently deleted :(
Hey @Alessa Leblanc Michel,
I'm sorry to hear that you accidentally deleted one of your boards. Permanent data loss can be devastating.
I work at Rewind, we're a backup and recovery app for SaaS applications. Very soon, we're going to be launching a solution to this problem with a Power-Up called Backups for Trello.
With Backups for Trello, you will be able to recover a deleted boards, lists, cards, attachments, and more by accessing the Rewind Vault that automatically captures a daily backup of the Trello boards storing your mission-critical data.
If you're interested, you can sign up for early access (and to stay updated about our launch) here.