How do I recover my phone contacts that were deleted when phone updated

Start by checking if Contacts is enabled in iCloud, go to:

Settings → Apple ID → iCloud. Check if Contacts is enabled in the list.

Also, make sure you're connected to a network so your iPhone can download your contacts back from iCloud.

If you have mistakenly deleted one or more contacts, they can possibly be restored, see here:

If you accidentally deleted your calendars, bookmarks, or contacts from iCloud - Apple Support