Lost my iPhone and Outlook Calendars-Can't restore iTunes Backup

I tried to sync an extra calendar onto my iPhone 12 running the latest software update. I've been using iTunes (12.13.1.3, know I'm a dinosaur) for backups on my MS PC.

I noticed that I lost all of my appointments on both my iPhone and PC when it last did a sync.

I thought no issue, I'll just go back and restore a backup from a few days ago. I plug in my phone via USB, in Summary see where I can manually restore and hit the button. First thing I get a pop up indicating that "Find My has to be turned off before my phone can be restored." I locate Find My Phone, but the toggle is grayed out and can't be moved.

Hopefully, someone can help me out! I have too many appointments lost to recreate. I'd appreciate any help I can get to prepare my phone and iTunes to restore an previous backup.

Thank you in advance!