If you are pan-frying fish (not sauteeing - that is different), the type of pan you use should not be your primary concern. Any pan wide enough to hold your fish should be sufficient. You could use nonstick or cast iron. Both will work if proper technique is used.
Here are things to consider:
Salmon will stick to almost anything, even non-stick surfaces, when it cooks. The secret to not winding up with ruined salmon is in the chemistry of the cooking process. After the maillard reactions in the meat progress, the surface of the fish that is in contact with the pan will begin to caramelize, and that caramelization will cause the fish to automatically detach from the pan. The pan should be pretty hot to accomplish this, and it's important not to move the fish in the pan until this happens, unless you want a mess on your hands.
When I pan fry salmon, I find that I don't need much fat. I will usually not add any fat to the pan and simply brush the salmon with some canola oil and grind on some salt and pepper before adding it to a hot pan. Butter can also work, but I would use clarified butter because of its higher smoke point.
Other things to consider include:
Are you making a fillet or a steak? These have different geometries and lend to different cooking methods.
Thickness of the pieces. You want to make sure that the inside cooks before the outside is overcooked. Thicker pieces may need to be pan fried on both sides and then finished in a hot oven. Thinner pieces, such as a sockeye salmon fillet, can be done on the grill or under the broiler entirely.
Do you know your target temperature? Salmon is done when it reaches ~130 F. Get a thermometer and insert it into the thickest part of the meat when you think it might be done.
Hopefully that helps somewhat!