It sounds like you have a threadless 1-1/8" fork so that takes care of the first spec. The other is the diameter of the handlebar at the clamp. With alloy drop bars it's usually 26mm, but might not be depending on the brand, so you should measure with a caliper right where it leaves the stem, or loosen the clamp and slide it over to be sure.

The 60mm, 80mm, etc refers to the length of the stem from center of the steerer to the center of the bar.

The angle definition is a bit tricky with most measuring the angle between the steerer and extension, and others giving the rise, which is the angle to the ground. When calculating rise they figure the steerer to be at 73°, so a 17° stem mounted with the small angle down would be horizontal, or have zero rise.

Other than matching the diameters at both ends, which is the correct stem for you depends on why you're replacing it in the first place. If you're trying to adjust the fit, you need to figure whether you want the bat farther or closer, higher or lower, and find the stem length and angle that gets it there. You can also fine tune the height by moving spacers from above the stem to below or vice versa.