Don't attempt to complete the forms until we explain what they are.
Then you will better understand what you need to write.
OK. The first form PE3 is straightforward.
You just tick the appropriate box, 'PCN not received.
In the 'reasons' box you can just write 'due to a change of address' or similar.
That is the Statutory Declaration but it is now too late to send it alone >>
You must also complete PE2 which is a request to file the PE3 late.
On this one you must clearly explain why it is late and back this up with whatever evidence you have. i.e. your move and the relevant dates and updating the V5C, with all detail.
I strongly suggest you post your draft here for review before you send it. It is very important to get it right because you application to TEC could be opposed by TfL and then it will be refused.
You will need to get the forms sworn/witnessed, as they explain.
Then we will give you the e-mail address to send them to.
As I explained in the Facebook group, you should pay the current amount demanded to avoid further fees.
Ask any questions you need to.