The drive has most likely been assigned a name such as sda, sdb, sdc, etc.
If the drive is partitioned, the partitions will have names like sda1, sda2, sdb1, sdb2, etc.
To see if TinyCoreLinux has recognised any drives/partitions do this: ls /dev/sda*
ls /dev/sdb*
[...etc]
To access the contents of a partition using linux you need to "mount" the partition. If, for example, you see /dev/sdb1 and /dev/sdb2 using the commands above, you can mount and list the contents of, for example, sdb2 like this: sudo mount /dev/sdb2
ls /mnt/sdb2
Note that, depending on whether the drive partition you want to access if formatted with a linux, windows or mac file system, you may need to take additional steps to be able to mount and read files on the partition.
Note also, if you have booted TinyCoreLinux from a usb stick, at least one partition on the usb stick will be already mounted. You can see which partition is mounted like this: ls -l /etc/sysconfig/tcedir
lrwxrwxrwx 1 root root 18 Jun 24 1970 /etc/sysconfig/tcedir -> /mnt/sdb2/tce/..where in this example partiton sdb2 is mounted