USB mount of Free BSD

Hello all

When I insert my USB , its says : umass0 detected . I want to ls files present in the USB.

I tried
mount -t msdosfs /dev/da0s1 /mnt

Whats is dev/da0s1 ?????
How can I mount it to use it ?

Regards

Filesystem mounting must be enabled for users (see Frequently Asked Questions for FreeBSD 12.X and 13.X | FreeBSD Documentation Portal#USER-FLOPPYMOUNT for a few examples)

sysctl vfs.usermount

/dev/da0s1 is supposed to be your USB flash drive filesystem, in your particular case, and assuming it's a regular flash drive (FAT32 formated, I mean)

Please see this source: Disk Organization
Once mounted, there is no message to say it has done so successfully. You can go to /mnt (ie, "cd /mnt") to see the contents of your flash drive.
To know what comes after the "-t", check this:

dmesg | grep da

You don't have enough rights to mount this device, either use vfs.usermount=1, or mount it as a root. More information you can find in handbook.