Your TV User Manual is located at
https
/www.manualslib.com/manual/550229/Lg-42ln5300.html
on page 23 of the manual (https

/www.manualslib.com/manual/550229/Lg-42ln5300.html?page=23#manual) it says
"Connect a USB storage device such as a USB flash memory, external hard drive, or a USB memory card reader to the TV"
but fails to mention what format your usb device should be in or what format the TV can read/play video with.
Later in Q&A it mentions to look in
"EXTERNAL CONTROL DEVICE SETUP" on Page 39 but that is not as helpful as one would believe.
To be honest the user manual for this television is pretty useless.
I would try to format your USB in FAT or FAT32 and see if it reads it. its pretty common settings, if your...