Modems are a little tricky, butthe other partition shouldn't be a problem. Become root by typing 'su'. You will then be prompted for the root password. Enter it. Then list out the partitions like this
# fdisk -l
Create a directory to mount the partition to.
# mkdir /mnt/fat
Then mount whichever one of the partitions showed up like this (if it is an FAT filesystem)
# mount -t msdos /dev/hdax /mnt/fat