I'm going to make a twin size Friendship quilt. So, it'll be appx 68x88 and I will use 3 or 4 different fabrics.

Do you think if I order 2 yards of each fabric that will be enough?

difficult to know without seeing the pattern/design.
But basially determine how much you need for each block and then number of blocks you need and multiply accordingly.

Add a bit extra for 'opps'.

44 X 36 = 1584 square inches
68 X 88 = 5984 sq inches
5984 \ 1584 = 3.78 yards for the top flat.

6 yards should be plenty even with opppps. As long as your pieces are not really small where you would need to add a percentage for seam allowances. The only other thing you need to determine is what percentage of each fabric you want the top to be.

I would count the number of blocks you need of each color and do the math. I have found that it always takes more that I think when all is said and done. I always buy extra because if I need more it is usually gone. That's how I got a huge stash. I recently made a baby quilt and used all different fabrics. It took me days to figure the yardage--probably 4-5 days on and off. I didn't run out of any of the fabrics. So I guess that it was time well spent.
Sue