ju take the battery, or drivw to an auto parts store or auto center and they will take care of it. it is probablly a d series being an older car. but it may have top and or side terminals either one. get about 650 cca battery at the smallest for good winter results.
a/c delco makes two size batteries that fits this car.The first is a group 58-6yr that has 560 cold cranking power.The second is a group 65-6yr that has 675 cold cranking power.First measure the dimensions of your battery and that will decide on which battery you can replace it.