You can easily create new keys/tokens for yourself by following these steps:
Once you have created a new key just copy and paste it into your Teamspeak 3 client to become a server administrator again.
The most common follow up questions is: My key/token says it is invalid or already used.
There are only 3 possiblites for this message popping up when you have just made a key. 99% of the time it is number 2.
The last one but really rare is: I can't use privilege keys. I disabled that permission
There are some idiotic guides out there that tell you to disable the use of keys by the guest group but that is pointless. There is no way to break or hack a key because they are unique to your location, and any attempt to brute force it would get them banned automatically. Even if they were to make attempts so slowly that they weren't banned it would take literally hundreds of years to guess a correct key. Whoever wrote those guides didn't know what they were talking about and nothing they write can be trusted. If this is the case the only way to get back admin status of your server would be to have another admin on your system give you your admin status back or reset the permissions of your server so that you can use keys again.