Ford Taurus Crankshaft Front Crankshaft Seal

I Have Bought 3 Different Seals From Autozone And Apparently They Were The Wrong Ones. Now I Can't Go By What Came Out Of The Vehicle...

How Do I Know If I Have A Front Seal Oil Leak Or A Main Rear Leak?all I Know Is There Is A Leak Because There's Oil On The Ground When I...