If you still have your Twixtor 3 key (which hopefully you do since you upgraded to version 4 and didn't start with version 4) you can install Twixtor 3 available here :
http://www.revisionfx.com/rstwixtordownloadsOldAE.htm .
You can then simply use Twixtor 3 or copy your settings to the twixtor 4 plugin (or better yet, link the values that are animated via expressions).
Pete Litwinowicz
http://www.revisionfx.com