So long as it's not over or under, you're ok. Keep in mind the dipstick level will change depending on whether the fluid is hot or cold - and also whether the trans is in Park/Neutral or Drive. If memory serves, you should check the level with the transmission warmed up and in Drive. (See your owner's manual to be sure.) You need a helper to do this safely, of course. One guy sits in the car with the transmission in gear and his foot on the brake; the other checks the level. You can do this by yourself if you are sure - I mean sure - the parking brake is in perfect working order and will hold the car when it's in gear for the minute or so it takes to check the level. But not recommended....
FYI: The TH350 in your car is one of GM's best-ever units and unless abused or not serviced every now and again will last as long as the car.