I have various folders with high res images sizes some more than 6000px x 4000px. some are 5000px x 3000px, size varies with folder to folder. I want to resize all images for saving resources like loading time/processing/memory space. I want to keep all images around minimum 3000x2000 max 3500x2200 . How I can do this with imagemagick in batch, Replacing original. Some one suggested my to use imagemagick with morgify on ubuntu?

Earlier when i had windows PC I used photosizer software. Selecting folder one by one, then process images with jpegMini software. So 5 mb photos decrease to the size to around 1.5 mb. Every folder contains images with different resolution. Its a long time consuming process.
For every folder i had to decrease % in fotosizer to keep image size around 3000\*2000 more or less maintaining aspect ratio.