See the docs: https://getbootstrap.com/docs/4.0/utilities/display/
In order to hide the content on mobile and display on the bigger devices you have to use the following classes:
d-none d-sm-block
The first class set display none all across devices and the second one display it for devices "sm" up (you could use md, lg, etc. instead of sm if you want to show on different devices.
I suggest to read about that before migration:
https://getbootstrap.com/docs/4.0/migration/#responsive-utilities