IS the USB cable actually a data cable (most are), and not purely a charging cable?
Have you transferred files successfully before with this or any other computer?
Is your tablet in Media Device (MTP) mode (rather than, say, PTP mode)?
Go to the Settings, storage. Click the options dropdown (3 dots, 3 bars or a dedicated button with 3 dots/bars on it). An option called "USB connection" will pop up. Tap that, you will go to a screen called "USB connection mode." Select MTP.
Note some computers don't support MTP. Conversely, some versions of Android do have another option on that screen saying "card reader mode" which fixes that.
I'm working from memory here, as a bunch of stuff changed around 4.2 to 4.4.