@ Sheli
Very sorry I entered in this thread very late. I have suggestion to make. Please open" Disks" from Menu Dash and you will find your Pen drive listed in the left side… Select it And Press Ctl+F. After that right click on the USB icon on the destop and you will have Format Menu as context Menu. Click it anf format will start. I found it working in Linux Mint 19.2.