Auto Resize Photos in Posting

Try to find answer from the old thread but couldn’t get what I want.

I have created the child theme. When I post my photos as Gallery, can I configure the post to auto resize all my image in Gallery to have a long edge of 600 pixel?

Or resize the image for all heigh maximum of 600 pixel?

I am looking for an alternative to have a consistency of photos viewing in the Gallery mode.

Example: https://www.chewhow.com/xiaoxuan-graphy/

When view in individual photos:
https://www.chewhow.com/xiaoxuan-graphy/5-oct-2013/#main

thanks in advance.