DC 12v 2a into DC 12v 3000aH
Here's how you decipher this, on a consumer product (which is almost always constant-voltage.) 

Voltage -- in Volts, coded V - should match. 12V... 12V.... You're ok. 

Current (Amperage) -- is measured in Amps, coded A.   Consumer products automatically draw as much current as they need, like a horse drinking as much water as it needs.  The device gives a worst case figure.  The supply must supply at least that much.  

The TV wants 3A - that was easy.  The supply gives 2000mA... Now that's an oddly large number, isn't it?  Has everything to do with the "m", which is the SI symbol for "milli" or 1/1000.  Like milligrams and millilitres, you must divide by 1000, so 2A.    The supply can't give enough power to run the TV.  Fail.  

AC/DC - the supply and appliance must match up on whether they use AC or DC.   The symbol for AC is a sinewave, DC is a solid line over a broken one (why???) 

If DC, polarity -- in DC, it matters which is positive or negative, there's a little diagram showing whether the center contact is positive or negative.  These must match. 

Fit - the connectors must fit, obviously.  Physicaly fitting does not mean the voltages are compatible, there is no standard for that.