How to recover contacts from backed up galaxy S2 (gingerbread) files
SIM contacts are not synced, neither are "phone" contacts. If you had used Google contact, they would have been synced with your Google/GMail account -- but then you wouldn't have noticed their loss, as they would have been synced back to your new device. Had you saved them as SIM contacts, they'd also be on your new device.

Which leaves us with the other non-synced variant: "phone contacts". Those are stored on device internal storage (to be more precise: in a database file located in /data/data/com.google.android.providers.contacts/databases), which is not directly accessible by normal users, so you could not have simply copied it.

Conclusion: as these data are not stored in "My Files", you have not copied them. And as you've factory-reset the original device, you cannot simply restore them from there. So apart from a quite expensive forensics recovery (done by a data recovery specialist) from your old device, there's no way to recover those contacts, sorry.