First, take a deep breath! It sounds like you originally started with all 2 1/2" squares for your 9 patch units, right? And now you have partially disassembled them into 'pieces' do you mean strips of 1, 2 and 3 squares? Look at the design your Aunt made and also look at google images for trip around the world quilts. I think the easiest way to proceed would be to lay out all your squares on a bed or a floor in pattern. You might have to disassemble some of your pieces to get the colors correct. Then start joining the squares into long rows. Press all the seams from the first row (and all odd rows) to the right, then press all the seams from the second (and all even # rows) to the left.
Take the first and second rows and put a pin at each intersection, matching seams as best you can. Sew the rows together & press to one side (doesn't matter which way). Continue joining the squares into long rows, pressing and adding the rows to the previously joined ones. Just take your time and it will be great.
If you want you can also google 'trip around the world quilt instructions' you will get lots of hits. Take a look and see if any of these help.