Welcome to MLS.
Just a note: the Whyte designation for a Mogul is 2-6-0; that trailing "0" has significance, telling that there are no trailing wheels. But, using the term "Mogul" does pretty much determine that your intent is the designation is a 2-6-0 so your question is understood, but just for completeness, be sure to specify all three wheel positions.
Same for the 4-4-0 (or American), that is 4 leading wheels, 4 Drive wheels and no trailing wheels; if you leave the trailing "0" off you cannot tell if it might be a 0-4-4 (which is a Forney).
BTW: The dashes also have meaning. The "-" indicates a flexible connection and a "+" is a rigid connection: if a loco is listed as a 4-4+2 then the trailing wheels are rigidly attached to the frame, whereas a 4-4-2 the trailing wheels are flexibly connected to the frame.
Just for our European friends, I should point out that they designate the arrangement by axle count, thus a Mogul is a 1-3-0.