This is assuming you have the original shoreland'r trailer. You can Google the part number highlighted and follow the Amazon links, what I don't get is why they call it a 9" fender? I know it shows 4 holes on the tread, that is how they attached the later fenders, not in the fender well like our trailers. I converted mine to mount like the later ones. I had a fender that ripped out and would float off the screws. You are going to have to get some dimensions, that is critical! I ordered a white plastic replacement fender once, it looked correct but dimensionally it was completely wrong, I returned it and changed the mounting like the new ones. You can also call shoreland'r, they are great people. I called a while back and asked if I could add disc brakes to my trailer, the guy took my vin and gave me the exact kit for my trailer, took him like 3 minutes to find it.
Any who, here's the parts diagram for the 99 trailer, should be the same as yours.
I would assume it's the correct fender, they both call out the 9", but I would just see if the seller can get you some dimensions, or if they will take a return