Since my update I lost reminders. How do you retrieve them.

If your reminder was synced with iCloud before your updated, turn on Reminders in Settings > [Your Name] > iCloud > Reminders to let it sync from cloud.

If you didn't have Reminders sync turned on before, you can only restore them if you have a backup on iTunes. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Patricia

I sincerely hope the article below assists you:

https://support.apple.com/en-us/HT205018