How to reset check engine light on 2003 Pontiac Bonneville ?? I don’t see a ECM OR ECU FUSE?

You can reset it by using a code reader or by disconnecting the negative battery cable for a few minutes.
I would first find out what code or codes it is showing.
There is a reason it went on and you should find out first why it went on.
It could be something serious that you should take care of.
Just because you reset the light does not mean the problem will go away.
Auto Zone or some parts stores usually will scan it for free for you.

How about #8 and #19 under the hood in fuse box.
Powertrain control module battery
Powertrain control module ignition.

That's on the 2003 leSabre per the owner manual pdf from their website.
The Bonneville should be the same. Verify with the list on the inside of the box cover.

An inexpensive code reader should have the ability to turn off the codes. It's worth the trouble.

Some of the box stores won't turn off code lights. They would just read them was my experience in the past.