Where is the trans filter located on 2011 subaru outback 5eat?

Unless there are problems with the transmission you do not need to do anything with transmission filter. Although I am not familiar with your specific transmission, Subaru includes a drain plug on the side of their transmissions. Drain fluid once a year and refill. Mine is the 4 speed and it takes 4 quarts to refill. This does not by any means remove all of the oil, but you will remove any sediment in the pan and will add fresh seal conditioners. Do this yearly and, barring abuse, your transmission will last the life of the car. Your transmission uses a special fluid that sells for about $5 to $8 a quart. Do not use standard Dexron type fluid.