H1B new employer new passport

Hi All, i had h1b stamp on my old passport with old employer, since then I changed my employer (got new approval notice ) and changed my passport as my old passport was about to expire.

Do i need to get a new stamp on my new passport as my old passport is expired and visa was on previous employer ?

You dont need new stamp if your visa is not expired, otherwise yes.
Note that even if the visa has employer’s name on it, it is not tied to any employer. It is just a travel document required to enter the US and can be used as far as it is valid, even if the stamp is in old expired passport, no issues.