If you were not the Flow creator or owner, then you might have not really deleted it - ask the Flow creator or owner to share it with you again. Also ask around if someone else has a backup of the same Flow somehow in case.
If you are sure you deleted a Flow that you created / owned and that you really need it back:
I do not believe there is any out of the box way to do this There is a possibility the Flow still exists somewhere for a temporary amount of time before it is ultimately permanently deleted - you can try and contact Microsoft Support to see if they have any options.
Check if below similar topics help, mainly regarding the instructions about how to contact Microsoft Support: