Hi @ViveLaChina
If you never went to a middle school here in the US, then I urge you to contact tamsadmissions@unt.edu immediately.
I had a similar problem in that I went to 2 different middle schools in Texas and the online portal was only accepting one report card submission. I contacted the aforementioned email, however, and they worked it out with me. So contact them ASAP so they can give you further instruction.
Hope this helps!