If you did a factory reset, the chances are that the entire file system was wiped, so there's no way a file undelete app can find anything to undelete. (And Christophe hasn't written PhotoRec for Android, so that won't do any good.) If you root the phone and dd the entire user partition for a file on a PC, you could try PhotoRec, but if you're capable of that you don't need any instructions or links from me, so I won't put any here. (It's not "push this click that", it's going deep into Linux, finding your user partition, then running dd to image it. Then finding the right database file, pulling it out and using a SQLite editor on it to get your contacts back. You're not going to learn that with a week of full-time study.) So if you can, good luck, but if you can't, let's hope all your contacts were Google contacts - if they were, they got backed up to contacts.google.com. If they're not there, go to "Switch to the old version". Then More (at the top), then "Restore contacts". You can restore anything deleted within the last 29 days.
(If they were Phone, Device or SIM contacts, they won't be there to restore.)