If for some reason the Format option is gone, then perhaps some of the firmware or settings have been drastically changed or worst, corrupted.
A couple of things you can try:
a. do a soft reset - press on the Power/Menu for 15 seconds;
b. do a full settings reset - Main Menu/Settings/Reset All;
c. do a Format - Main Menu/Settings/Format but all in the internal memory will be erased;
If the above will not work, you can also try:
1. download and run in your PC Sansa Connect Recovery Tool
2. read the How to use the Sansa Connect Recovery Tool
and follow the instructions carefully;
doing #1 will erase the corrupted files, unfortunately so with everything else. It will then restore the device software to an
Hope this be of help/ Pls post back how things turned up or should you need additional information.
Good luck and kind regards.