Break these loose, then re-tighten, before you take the car to a mechanic for 4-wheel alignment. Do one bolt at a time, to avoid messing up the adjustment any further than it already is. The adjustment is done by moving the outer end of the axle towards the front or rear of the car. The holes on the spring plate where the bolts go through, are strongly ovalled to allow adjustment. This adjustment is generally done with the help of a big hammer.
In the front, you should clean and re-grease the front wheel bearings, and tighten them to spec before alignment can be done. If there's too much play in the wheel bearings, the alignment tool readings will be off. (Wasted money). Also break the tie rod ends and lock nuts loose in the front, and retighten, before taking the car to the shop. You'll be spending a full weekend with these little items if you are unlucky, and you don't want to pay the mechanic for the time he has to spend trying to break rusty bolts and nuts loose. He doesn't want to waste time on them either. Better do this all in advance.