Unable to open document created using Creo Parametric version 6 in new version 7

I had previously downloaded the free version on the PTC Creo Parametric software, student edition version 6. I had also created a few of the drawings and parts using the software. Due to some personal work, I couldn't open those documents for more than 3 months. Once I tried to open now, a pop up banner read, new version available and I'll have to mandatorily download the new version. I did the same and I'm unable to open the files I created using the version 6 software from the version 7 software. I need to edit a few things in the file and I'm unable to open any of those files. Please Help.