If your axles have one end with I think it is 5 or six bolts and on the other end of the axle where the boot attaches looks somewhat like a Can you have an "Annular" type axles on your car.
The other type of "Homokinetic" axles have a Can on both ends of the axle and no visable bolts. The Homokinetic axles rebuilt or new seem to cost less and the manual claims both will work on your car. My 84 300D has the Homokinetic axles.
See if your mechanic is able to find out why the axle came out. I am curious to know if it was a failure of something inside of the differential or if the it was the CV joint that went bad first.

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84 300D, 82 Volvo 244Gl Diesel