how do you recover contacts on iphone SE some were lost during latest update

Contacts on your phone are associated with email accounts. Each email account hosts some contacts on the phone (if you have more than one, of course). So first make sure you haven’t disabled any email addresses.

Next, open Contacts. Do you see the word Groups in the upper left corner? If you do tap on it and make sure all groups are checked.

If you are specifically missing iCloud contacts, and you sync contacts with iCloud (Settings/[your name]/iCloud - Contacts ON) log in to https://icloud.com, tap on Settings, then Advanced at the bottom and there is an option to recover contacts. Here are some details—>Restore contacts, calendars, bookmarks, and more using iCloud.com - Apple Support

What were you syncing them with?