[ubuntu] transfer music directories from Ubuntu desktop to Android Samsung Galaxy S7

HI Community:

I bought an Android Samsung Galaxy S7 ... and put a 64Gb microSDXC card to augment its capacity. It is a new model Android, so it probably has the most recent Android operating system.... I don't know much about that.

I want to transfer music directories on my Ubuntu desktop that have music to the Android.

When I plug the Android into my Ubuntu desktop I don't see anything... no directories or anything.

Can somebody tell me how to transfer those music directories from my Ubuntu desktop to my Android's microSDXC card so that I can see them on the Android and play them?

Many thanks,
Old Jimma