Hello! Unfortunately, once you have deleted messages on Facebook, they are permanently deleted and cannot be recovered. However, there are some things you can try:
1. Check your archived messages: Sometimes, instead of deleting messages, we accidentally archive them. To check your archived messages, go to the Messages section on Facebook and click on "More" in the left-hand menu. Then, click on "Archived." If your deleted messages were actually just archived, you may be able to find them here.
2. Contact Facebook Support: If you believe your deleted messages were important and you desperately need them back, you can try contacting Facebook support. While there is no guarantee that they will be able to help you, it's worth a shot.
3. Use a third-party data recovery tool: There are some third-party data recovery tools that claim to be able to recover deleted messages from Facebook. However, be very cautious when using these tools, as they could potentially be scams or even infect your computer with malware.
Overall, the best way to ensure that you don't lose important messages in the future is to regularly back them up or save them elsewhere. Good luck!