How to retrieve deleted contacts

If you were using iCloud contacts:

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

If not, you will have to restore your device from a backup that had those contacts:

Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

Be aware that restore is an all or nothing process. You cannot restore only contacts (for example) and any information on your device between now and when the backup was created will be lost.

If you're logged in to https://icloud.com, on the very top right (of the home screen) or the very top left (if in any of the web apps) there is a menu. From the home screen that menu is your first name. From in any of the web apps, it starts with "iCloud".

Click on "Account Settings". On the Account Settings page, at the very bottom, there are a bunch of "Restore" options, including "Restore Contacts".

Go to iCloud.com and under Account Settings see Advanced Restore Contacts.

Did you scroll down all the way? Do you see a "Sign out of all browers" option in the Settings (https://www.icloud.com/settings/).