Welcome to Android Central. What device do you have, and what version of Android is it running? Was Samsung Music preinstalled or did you install it from Galaxy Store? I'm asking because I've never had or used Samsung Music. It wasn't preinstalled on my devices, and I've always used Poweramp for my locally stored music files.
• On my s22 Ultra.
• Installed from the Galaxy Store.
• This may or may not help in your case , as the answers to the questions that @Laura Knotek asked would be helpful.
In the Samsung Music App:
~Go to your Folder Tab
~Select the folder you want
~The list of music included in that folder will be displayed.
If you do not see a Folder tab, go to settings in the drop down menu in the upper right corner of Samsung & you can organize the tabs. You can make playlists in Samsung Music which can make things easier.