confused

had an L1b visa but said it expired in a year and I read online these are good for minimum of 3 yrs? and can be extended. What is the process to extend it?

Your original employer needs to extend it. See them.

can it be renewed if it expired years ago?

Obce you've left US for a year, you can re-start the entire L1 process.

But you need to have been recently employed by a relative firm, just like 10 years ago.

Your old L1 is of no use anymore.

Again, this is an issue for your employer. They initiate the transfer to US