How can I retrieve my telephone numbers on iphone

The following link has instructions on how to restore using an iTunes or iCloud backup. Note that a restore will replace all of the data on your phone with the data from the time of the backup. There isn't a way to restore just Contacts from a backup. Restore your iPhone, iPad, or iPod touch from a backup - Apple Support

If you had the Contacts synced to iCloud (i.e., if Settings > iCloud > Contacts was turned on), you can use a computer and log in to https://www.icloud.com/ and then go to the Settings app there and in the Advanced section at lower left there is an option to Restore Contacts. Using that will allow you to select an archive date and will then restore your Contacts on all of your devices that have Contact sync turned on. It will also make a new archive of the contacts before it does the restore.

from backup?

Restore your device from an iCloud or iTunes backup - Apple Support

Apr 5, 2016 - Follow these steps if you need help restoring your iPhone, iPad, or iPod touch from an iTunes backup. For example, there might not be a ...

Note that an ICloud backup does not include contacts, or any other data that is already stored in your iCloud. Contacts can be sync'd across devices using iCLoud, but if you did not enable contacts in your iPhone's iCLoud settings, then they will not be in iCloud at all. If you have an iTunes backup, you can use that.

About backups in iCloud and iTunes - Apple Support

If you have iCloud sync enabled for contacts, and you deleted those numbers, then they will have been deleted in iCloud as well as the whole point of iCloud sync is to keep your contacts synchronized across all devices sharing that iCloud account. Unless you have an iTunes backup, or keep a separate copy of your contacts on your computer or somewhere, then sorry, but they are gone.