2011 F-350 SD 6.7 diesel fuel filters?

One is under the hood-driver side firewall at the top. Look and you'll see it. The other is under the driver's seat on the bottom of the truck. It's where you drain water from the fuel system. Look on YouTube and you'll find some videos showing how to change the filters.

Also check the priming instructions in the driver's manual diesel supp.

You can find third party versions on Amazon, but it wasn't a lot cheaper.

Last word: the housing on the under the truck filter has to be tightened way past the point where you'll be worried that you are going to snap off the plastic fitting. It has to to go around until it hits a positive stop. Failure to get it tight enough means you will not get the fuel system primed. IIRC you need an 1 1/4 inch socket on a cheater bar to pull it up.

Dieselfiltersonline
Read owners manual
Check out the Ford truck forums

Where they are? No clue unless you look.
Where to purchase them? Lots of places online. BTW you do not need to purchase Motorcraft branded filters. As long as they meet Ford standards you are golden.