Each pack of Microgynon should give you 3 weeks of active tablets (21 days). Assuming you ran two packs together, I suppose that you skipped the fourth week of inactive tablets and went right again to the active tablets in the second pack. This should have given you 6 total weeks of tablets, and you are right that you should have ended on the same day you started. The fact that you did not means that you must have accidentally skipped some pills or miscounted.
I think what to do next depends a lot on what your normal use of Microgynon is like and what your primary care doctor
recommends. For example, if you, with the help of your doctor, are running multiple packs together to skip periods, then what to do depends on whether it is time for you to have a period or not. If you do not take any more pills right now, you should have a period, but then restarting the pills again will require you to have another prescription on hand.
Therefore, start by contacting your primary care doctor (or whichever doctor prescribed the pills for you) and explaining the situation to them. They will be able to help. Good luck!