Reformat MicroSD card in LG used originally in Samsung?

Just curious...
I took out a microSD card from my Samsung SCH-a930 and placed it into my
LG-VX8300. The memory card does not need to be re-formatted in the LG does
it?

Also, when I checked the memory usage on the sd card in the LG it said
there was 976K used. I have no idea what 976K is made up of (data). How do
I find out what is taking up the space on the sd card?

Walter