I can not finish set up for my ipad because of i do not remember apple ID what I registered before time?

Hello Apple,

I'm in Viet Nam and I bought Ipad when I came to USA.

When set up ipad, I filled some information what include Apple ID. Using is OK and I set up password for Ipad, and then I loss password, i bring it to shop, they unlock pass but request apple ID. I provide my apple ID but can not do. Now I can not use my Ipad.

Pls help to instruct me how to do now.

Thank you.