XnView has batch processing. It's super easy to use and it's free. Basically open the batch processing window, click on the few various functions you want to have performed and then select the size of the final images. It's as easy as I've seen.Do you have Adobe Photoshop?
Within Photoshop you can set up batch jobs: https://www.digitalartsonline.co.uk/tutorials/photoshop/how-resize-multiple-images-in-photoshop/
If you don't have Photoshop, you coud try this: https://www.diytechguides.com/resize-multiple-images-at-once-in-windows-10/
https://www.xnview.com/en/