1986 Chevy Celebrity

Welcome to the forum. I'd take the old rotor off and take it to autostore to compare. One is heavy duty the other isn't. I don't know which one you have?

jdl123 suggestion is good, match them up to be sure.
If you can not, if this is your only transportation than you'll have to go by the code.
JA1 is the standard brake system, used on the majority of sedans, JA2 is the HD brake system used on most station wagons, some sedans and the Euro version. THere sould be an option code label, found in the glove compartment or trunk. It's a white lable about 3" x 4" with a black stripe at the top. it will say SPO or service parts options on it and have several rows of 3 character codes on it in alph-numerical order.
if you can't find the lable measure the bolt pattern, the JA1 system has a smaller bolt pattern than the JA2 system.
Hope this helps, let me know.
Dan