If you entered them as Google contacts, go to Google Contacts, More, Restore contacts. You can restore anything that's been deleted during the past month.
If they were entered as Phone, Device or SIM contacts, they're gone and you'll have to enter them again. (And this time, enter them as Google contacts.)
In addition to what Rukbat told you there may be a setting to display all contacts from different sources. As an example some of my contacts used to be stored on Verizon. Might not be your case but it doesn't hurt to mention it.