If your TJ is stock and not a Rubicon model, its gonna have a D30 front. Rear is probably a D35, but could have been ordered with a D44.
They do put tags on the that show the ratio, bit over time can fall off, or get lost during lube changes, etc. On the D30, the tag is between 2 diff cover bolts on the LH side. The ratio is the first number on the second row.
Compare your front axle cover to the rear. If the rear is a lot bigger, its a D44. If its a small oval, its a D35. There are pics online showing the different diff. covers.