After I-140 is approved, how soon I can join new employer?

[a100]

My green card is applied in EB3 category and PD is 2010. I have not filed I-485 concurrently.

After I-140 is approved, how soon I can join new employer and also get 3 years extension and be able to port PD with new employer? In other words: can I change my current job as soon as my I-140 is approved or do I have to first file I-485 and wait for 180 days and then join new employer to be able get 3 years extension and be able to port PD with new employer?

Thanks