Ensure the last backup happened before you deleted the messages.
Turn off the internet on your PC immediately, open BOTIM, and manually copy or screenshot the important conversations before the app syncs the deletion. ⚠️ A Note on Third-Party Recovery Software
Go to Settings > [Your Name] > iCloud > Manage Storage > Backups.
If you use an iPhone and had enabled, your BOTIM data is likely stored in your general phone backup.