Recover or reset pin code on ZTE z992

I've bought a gophone zte z992 in 2014 and used it for a month, during a trip to Disney with my only son. After that I went back to Brazil, where I live and never used it since.

My son died and I'm trying to recover all the old memories I can find.

But I can't remember my PIN code for this phone.

I already contacted the unlock phone fomr AT&t and received an unlock code, but that is not the PIN I need.

Unfornately, the email account that I've used when I bought it does not exist anymore, because the provider stopped working. Therefore, I can't try to access the at&t account.

Can you help me, please??