I started a DP9 and cut 22 8 inch squares. I have them finished and wanted to know how many 9 patches I need for a large quilt. I am a very new quilter.

You can search for a tutu here on this board and see what you come up with.

start with the size quilt you want, then multiply 8 inches times how many to get across the bed and then down. like 8x10 blocks would be eighty blocks. if not large enough, multiply more blks and you will have it.
depends too on if you want borders or not. if you do, you only have to have enough blocks to cover the top of the mattress.