I stopped wearing my retainer 2-3 years ago

Hello,
Since you are unable to locate your previous Invisalign provider, I would recommend that you see a new dentist who provides Invisalign treatment and they should be able to provide you with new retainers. Your records will still be in the system with the company but your dentist will most likely take new impressions for new retainers since you have not worn your retainers for 2-3 years so some change in tooth position would have occurred. Also, if you look carefully, there are numbers on the Invisalign trays so if you know how many trays were a part of your treatment, you should be able to figure out which was your last aligner. That way you can check if it fits. 

Unfortunately you can't move your teeth back to perfect position by wearing old trays again, because most probably your teeth are not in exact position as they were few years ago.
I would recommend to see an invisalign provider as soon as possible, you might be able to correct the issue with Express 5 or 10. Good luck!